Fenestrated Sheath For Embolic Protection During Transcarotid Carotid Artery Revascularization

ABSTRACT

Methods, devices, and systems establish and facilitate retrograde or reverse flow blood circulation in the region of the carotid artery bifurcation in order to limit or prevent the release of emboli into the cerebral vasculature such as into the internal carotid artery. The methods are particularly useful for interventional procedures, such as stenting and angioplasty, atherectomy performed through a transcarotid approach or transfemoral into the common carotid artery, either using an open surgical technique or using a percutaneous technique, such as a modified Seldinger technique or a micropuncture technique.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to co-pending U.S. Provisional PatentApplication Ser. No. 62/580,869 filed on Nov. 2, 2017 and entitled“FENESTRATED SHEATH FOR EMBOLIC PROTECTION DURING TRANSCAROTID CAROTIDARTERY REVASCULARIZATION”. Priority of the aforementioned filing date isclaimed and the disclosure of the provisional patent application ishereby incorporated by reference in its entirety.

BACKGROUND

The present disclosure relates generally to medical methods and devices.More particularly, the present disclosure relates to devices for useduring carotid arterial vasculature and establishing retrograde bloodflow during performance of carotid artery stenting and other procedures.

Carotid artery disease usually consists of deposits of plaque P whichnarrow the junction between the common carotid artery CCA and theinternal carotid artery ICA, an artery which provides blood flow to thebrain (FIG. 5). These deposits increase the risk of embolic particlesbeing generated and entering the cerebral vasculature, leading toneurologic consequences such as transient ischemic attacks TIA, ischemicstroke, or death. In addition, should such narrowings become severe,blood flow to the brain is inhibited with serious and sometimes fatalconsequences.

Two principal therapies are employed for treating carotid arterydisease. The first is carotid endarterectomy CEA, an open surgicalprocedure which relies on occluding the common, internal and externalcarotid arteries, opening the carotid artery at the site of the disease(usually the carotid bifurcation where the common carotid artery CCAdivides into the internal carotid artery ICA and external carotid arteryECA), dissecting away and removing the plaque P, and then closing thecarotid artery. The second procedure relies on stenting of the carotidarteries, referred to as carotid artery stenting CAS, typically at oracross the branch from the common carotid artery CAA into the internalcarotid artery ICA, or entirely in the internal carotid artery. Usually,a self-expanding stent is introduced through percutaneous puncture intothe femoral artery in the groin and up the aortic arch into the targetcommon carotid artery CCA.

In both these approaches, the patient is at risk of emboli beingreleased into the cerebral vasculature via the internal carotid arteryICA. The clinical consequence of emboli release into the externalcarotid artery ECA, an artery which provides blood to facial structures,is less significant. During CEA, the risk of emboli release into theinternal carotid artery ICA is minimized by debriding and vigorouslyflushing the arteries before closing the vessels and restoring bloodflow. During the procedure while the artery is opened, all the carotidarteries are occluded so particles are unable to enter the vasculature.

In carotid stenting CAS procedures, adjunct embolic protection devicesare usually used to at least partially alleviate the risk of emboli. Anexample of these devices are distal filters, which are deployed in theinternal carotid artery distal to the region of stenting. The filter isintended to capture the embolic particles to prevent passage into thecerebral vasculature. Such filtering devices, however, carry certainlimitations. They must be advanced to the target vessel and cross thestenosis prior to deployment, which exposes the cerebral vascular toembolic showers; they are not always easy to advance, deploy, and removethrough a tight stenosis and/or a severely angulated vasculature; andfinally, they only filter particles larger than the filter pore size,typically 100 to 120 nm. Also, these devices do not filter 100% of theflow due to incomplete wall opposition of the filter, and furthermorethere is a risk of debris escape during filter retrieval.

Of particular interest to the present disclosure, an alternative methodfor reducing the risk of emboli release into the internal carotid arteryICA has been proposed for use during carotid stenting CAS proceduresutilizing the concept of reversing the flow in the internal carotidartery ICA to prevent embolic debris entering the cerebral vasculature.Although a number of specific protocols have been described, theygenerally rely on placing a sheath via the femoral artery (transfemoralaccess) into the common carotid artery. Flow in the common carotidartery is occluded, typically by inflating a balloon on the distal tipof the sheath. Flow into the external carotid artery ECA may also beoccluded, typically using a balloon catheter or balloon guidewireintroduced through the sheath. The sheath is then connected to a venouslocation or to a low pressure external receptacle in order to establisha reverse or retrograde flow from the internal carotid artery throughthe sheath and away from the cerebral vasculature. After such reverse orretrograde flow is established, the stenting procedure may be performedwith a greatly reduced risk of emboli entering the cerebral vasculature.

An alternate system which simply halts forward flow in the ICA consistsof a carotid access sheath with two integral balloons: an ECA occlusionballoon at the distal tip, and a CCA occlusion balloon placed some fixeddistance proximal to the ECA balloon. Between the two balloons is anopening for delivery of the interventional carotid stenting devices.This system does not reverse flow from the ICA to the venous system, butinstead relies on blocking flow and performing aspiration to removeembolic debris prior to establishing forward flow in the ICA.

While such reverse or static flow protocols for performing stenting andother interventional procedures in the carotid vasculature hold greatpromise, such methods have generally required the manipulation ofmultiple separate access and occlusion components. Moreover, theprotocols have been rather complicated, requiring many separate steps,limiting their performance to only the most skilled vascular surgeons,interventional radiologists and cardiologists. In addition, due to thesize limitations of the femoral access, the access devices themselvesprovide a very high resistance to flow, limiting the amount of reverseflow and/or aspiration possible. Furthermore, the requirement to occludethe external carotid artery adds risk and complexity to the procedure.The balloon catheter for occluding the external carotid artery canbecome trapped in the arterial wall in cases where the stent is placedacross the bifurcation from the common carotid artery to the internalcarotid artery, and may cause damage to the deployed stent when it isremoved.

None of the cerebral protection devices and methods described offerprotection after the procedure. However, generation of embolic particleshas been measured up to 48 hours or later, after the stent procedure.During CEA, flushing at the end of the procedure while blocking flow tothe internal carotid artery ICA may help reduce post-procedure emboligeneration. A similar flushing step during CAS may also reduce embolirisk. Additionally, a stent which is designed to improve entrapment ofembolic particles may also reduce post-procedure emboli.

In addition, all currently available carotid stenting and cerebralprotection systems are designed for access from the femoral artery.Unfortunately, the pathway from the femoral artery to the common carotidartery is relatively long, has several turns which in some patients canbe quite angulated, and often contains plaque and other diseases. Theportion of the procedure involving access to the common carotid arteryfrom the femoral artery can be difficult and time consuming as well asrisk generating showers of embolic debris up both the target and theopposite common carotid artery and thence to the cerebral vasculature.Some studies suggest that up to half, or more, of embolic complicationsduring CAS procedures occur during access to the CCA. None of theprotocols or systems offer protection during this portion of theprocedure.

Recently, a reverse flow protocol having an alternative access route tothe carotid arteries has been proposed by Criado. This alternative routeconsists of direct surgical access to the common carotid artery CCA,called transcervical or transcarotid access. Transcarotid access greatlyshortens the length and tortuosity of the pathway from the vascularaccess point to the target treatment site thereby easing the time anddifficulty of the procedure. Additionally, this access route reduces therisk of emboli generation from navigation of diseased, angulated, ortortuous aortic arch or common carotid artery anatomy.

The Criado protocol is described in several publications in the medicalliterature cited below. As shown in FIG. 3, the Criado protocol uses aflow shunt which includes an arterial sheath 210 and a venous sheath212. Each sheath has a side arm 214, terminating in a stopcock 216. Thetwo sheaths stopcocks are connected by a connector tubing 218, thuscompleting a reverse flow shunt from the arterial sheath 210 to thevenous sheath 212. The arterial sheath is placed in the common carotidartery CCA through an open surgical incision in the neck below thecarotid bifurcation. Occlusion of the common carotid artery CCA isaccomplished using a temporary vessel ligation, for example using aRummel tourniquet and umbilical tape or vessel loop. The venous returnsheath 212 is placed in the internal jugular vein IJV (FIG. 3), also viaan open surgical incision. Retrograde flow from the internal carotidartery ICA and the external carotid artery ECA may then be establishedby opening the stopcock 216. The Criado protocol is an improvement overthe earlier retrograde flow protocols since it eliminates the need forfemoral access. Thus, the potential complications associated with thefemoral access are completely avoided. Furthermore, the lower flowrestrictions presented by the shorter access route offer the opportunityfor more vigorous reverse flow rate, increasing the efficiency ofembolic debris removal. Because of these reduced flow restrictions, thedesired retrograde flow of the internal carotid artery ICA may beestablished without occluding the external carotid artery ECA, asrequired by the earlier protocols.

While a significant improvement over the femoral access-based retrogradeflow protocols, the Criado protocol and flow shunt could still benefitfrom improvement. In particular, the existing arterial and venoussheaths used in the procedure still have significant flow restrictionsin the side arms 214 and stopcocks 216. When an interventional catheteris inserted into the arterial access sheath, the reverse flow circuitresistance is at a maximum. In some percentage of patients, the externalcarotid artery ECA perfusion pressure is greater than the internalcarotid artery ICA perfusion pressure. In these patients, thisdifferential pressure might drive antegrade flow into the ICA from theECA. A reverse flow shunt with lower flow resistance could guaranteereversal of flow in both the ECA and ICA despite a pressure gradientfrom the ECA to the ICA.

In addition, there is no means to monitor or regulate the reverse flowrate. The ability to increase and/or modulate the flow rate would givethe user the ability to set the reverse flow rate optimally to thetolerance and physiology of the patient and the stage of the procedure,and thus offer improved protection from embolic debris. Further, thesystem as described by Criado relies on manually turning one or morestopcocks to open and close the reverse flow shunt, for example duringinjection of contrast medium to facilitate placement of the CAS systems.Finally, the Criado protocol relies on open surgical occlusion of thecommon carotid artery, via a vessel loop or Rummel tourniquet. A systemwith means to occlude the common carotid artery intravascularly, forexample with an occlusion element on the arterial access sheath, wouldallow the entire procedure to be performed using percutaneoustechniques. A percutaneous approach would limit the size and associatedcomplications of a surgical incision, as well as enable non-surgicalphysicians to perform the procedure.

For these reasons, it would be desirable to provide improved methods,apparatus, and systems for performing transcarotid access, retrogradeflow and flushing procedures and implantation of a carotid stent in thecarotid arterial vasculature to reduce the risk of procedural andpost-procedural emboli, to improve the level of hemostasis throughoutthe procedure, and to improve the ease and speed of carotid arterystenting. The methods, apparatus, and system should simplify theprocedure to be performed by the physician as well as reduce the risk ofimproperly performing the procedures and/or achieving insufficientretrograde flow and flushing to protect against emboli release. Thesystems should provide individual devices and components which arereadily used with each other and which protect against emboli-relatedcomplications. The methods and systems should also provide forconvenient and preferably automatic closure of any and all arterialpenetrations at the end of the procedure to prevent unintended bloodloss. Additionally, the systems, apparatus, and methods should besuitable for performance by either open surgical or percutaneous accessroutes into the vasculature. Additionally, the methods, apparatus, andsystems should enable implantation of an intravascular prostheticimplant which lowers post procedural complications. At least some ofthese objectives will be met by the inventions described herein below.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a schematic illustration of a retrograde blood flow systemincluding a flow control assembly wherein an arterial access deviceaccesses the common carotid artery via a transcarotid approach and avenous return device communicates with the internal jugular vein.

FIG. 1B is a schematic illustration of a retrograde blood flow systemwherein an arterial access device accesses the common carotid artery viaa transcarotid approach and a venous return device communicates with thefemoral vein.

FIG. 1C is a schematic illustration of a retrograde blood flow systemwherein an arterial access device accesses the common carotid artery viaa transfemoral approach and a venous return device communicates with thefemoral vein.

FIG. 1D is a schematic illustration of a retrograde blood flow systemwherein retrograde flow is collected in an external receptacle.

FIG. 2A is an enlarged view of the carotid artery wherein the carotidartery is occluded with an occlusion element on the sheath and connectedto a reverse flow shunt, and an interventional device, such as a stentdelivery system or other working catheter, is introduced into thecarotid artery via an arterial access device.

FIG. 2B is an alternate system wherein the carotid artery is occludedwith a separate external occlusion device and connected to a reverseflow shunt, and an interventional device, such as a stent deliverysystem or other working catheter, is introduced into the carotid arteryvia an arterial access device.

FIG. 2C is an alternate system wherein the carotid artery is connectedto a reverse flow shunt and an interventional device, such as a stentdelivery system or other working catheter, is introduced into thecarotid artery via an arterial access device, and the carotid artery isoccluded with a separate occlusion device.

FIG. 2D is an alternate system wherein the carotid artery is occludedand the artery is connected to a reverse flow shunt via an arterialaccess device and the interventional device, such as a stent deliverysystem, is introduced into the carotid artery via a separate arterialintroducer device.

FIG. 3 illustrates a prior art Criado flow shunt system.

FIG. 4 illustrates a normal cerebral circulation diagram including theCircle of Willis.

FIG. 5 illustrates the vasculature in a patient's neck, including thecommon carotid artery CCA, the internal carotid artery ICA, the externalcarotid artery ECA, and the internal jugular vein IJV.

FIG. 6A illustrates an arterial access device useful in the methods andsystems of the present disclosure.

FIG. 6B illustrates an additional arterial access device constructionwith a reduced diameter distal end.

FIGS. 7A and 7B illustrate a tube useful with the sheath of FIG. 6A.

FIG. 7C show an embodiment of a sheath stopper.

FIG. 7D shows the sheath stopper of FIG. 7C positioned on a sheath.

FIGS. 7E and 7F show the malleable sheath stopper in use.

FIG. 7G shows an embodiment of a sheath with a flexible distal segmentand a sheath stopper in use.

FIG. 8A illustrates an additional arterial access device constructionwith an expandable occlusion element.

FIG. 8B illustrates an additional arterial access device constructionwith an expandable occlusion element and a reduced diameter distal end.

FIGS. 9A and 9B illustrate an additional embodiment of an arterialaccess device.

FIGS. 9C and 9D illustrate an embodiment of a valve on the arterialaccess device.

FIGS. 10A through 10D illustrate embodiments of a venous return deviceuseful in the methods and systems of the present disclosure.

FIG. 11 illustrates the system of FIG. 1 including a flow controlassembly.

FIGS. 12A-12B illustrate an embodiment of a variable flow resistancecomponent useful in the methods and systems of the present disclosure.

FIGS. 13A-13D illustrate an embodiment of a fenestrated sheath.

FIGS. 14A-14E illustrate the exemplary blood flow paths during aprocedure for implanting a stent at the carotid bifurcation inaccordance with the principles of the present disclosure.

DETAILED DESCRIPTION

The disclosed methods, apparatus, and systems establish and facilitateretrograde or reverse flow blood circulation in the region of thecarotid artery bifurcation in order to limit or prevent the release ofemboli into the cerebral vasculature, particularly into the internalcarotid artery. The methods are particularly useful for interventionalprocedures, such as stenting and angioplasty, atherectomy, performedthrough a transcarotid approach or transfemoral into the common carotidartery, either using an open surgical technique or using a percutaneoustechnique, such as a modified Seldinger technique or a micropuncturetechnique.

Access into the common carotid artery (FIG. 5) is established by placinga sheath or other tubular access cannula into a lumen of the artery,typically having a distal end of the sheath positioned proximal to thejunction or bifurcation B from the common carotid artery to the internaland external carotid arteries. The sheath may have an occlusion memberat the distal end, for example a compliant occlusion balloon. A catheteror guidewire with an occlusion member, such as a balloon, may be placedthrough the access sheath and positioned in the proximal externalcarotid artery ECA to inhibit the entry of emboli, but occlusion of theexternal carotid artery is usually not necessary. A second return sheathis placed in the venous system, for example the internal jugular veinIJV or femoral vein FV. The arterial access and venous return sheathsare connected to create an external arterial-venous shunt.

Retrograde flow is established and modulated to meet the patient'srequirements. Flow through the common carotid artery is occluded, eitherwith an external vessel loop or tape, a vascular clamp, an internalocclusion member such as a balloon, or other type of occlusion means.When flow through the common carotid artery is blocked, the naturalpressure gradient between the internal carotid artery and the venoussystem will cause blood to flow in a retrograde or reverse directionfrom the cerebral vasculature through the internal carotid artery andthrough the shunt into the venous system.

Alternately, the venous sheath could be eliminated and the arterialsheath could be connected to an external collection reservoir orreceptacle. The reverse flow could be collected in this receptacle. Ifdesired, the collected blood could be filtered and subsequently returnedto the patient during or at the end of the procedure. The pressure ofthe receptacle could be open to atmospheric pressure, causing thepressure gradient to create blood to flow in a reverse direction fromthe cerebral vasculature to the receptacle or the pressure of thereceptacle could be a negative pressure.

Optionally, to achieve or enhance reverse flow from the internal carotidartery, flow from the external carotid artery may be blocked, typicallyby deploying a balloon or other occlusion element in the externalcarotid just above (i.e., distal) the bifurcation within the internalcarotid artery.

Although the procedures and protocols described hereinafter will beparticularly directed at carotid stenting, it will be appreciated thatthe methods for accessing the carotid artery described herein would alsobe useful for angioplasty, artherectomy, and any other interventionalprocedures which might be carried out in the carotid arterial system,particularly at a location near the bifurcation between the internal andexternal carotid arteries. In addition, it will be appreciated that someof these access, vascular closure, and embolic protection methods willbe applicable in other vascular interventional procedures, for examplethe treatment of acute stroke.

The present disclosure includes a number of specific aspects forimproving the performance of carotid artery access protocols. At leastmost of these individual aspects and improvements can be performedindividually or in combination with one or more other of theimprovements in order to facilitate and enhance the performance of theparticular interventions in the carotid arterial system.

In one aspect, there is disclosed a system for use in accessing andtreating a carotid artery. The system comprises an arterial accessdevice adapted to be introduced into a common carotid artery and receiveblood flow from the common carotid artery; a shunt fluidly connected tothe arterial access device, wherein the shunt provides a pathway forblood to flow from the arterial access device to a return site; and aflow control assembly coupled to the shunt and adapted to regulate bloodflow through the shunt between at least a first blood flow state and atleast a second blood flow state, wherein the flow control assemblyincludes one or more components that interact with the blood flowthrough the shunt.

In another aspect, there is disclosed a system for use in accessing andtreating a carotid artery. The system comprises an arterial accessdevice adapted to be introduced into a common carotid artery and receiveblood flow from the common carotid artery; a shunt fluidly connected tothe arterial access device, wherein the shunt provides a pathway forblood to flow from the arterial access device to a return site; a flowmechanism coupled to the shunt and adapted to vary the blood flowthrough the shunt between a first blood flow rate and a second bloodflow rate; and a controller that automatically interacts with the flowmechanism to regulate blood flow through the shunt between the firstblood flow rate and the second blood flow rate without requiring inputfrom a user.

In another aspect, there is disclosed a device for use in accessing andtreating a carotid artery. The device comprises a distal sheath having adistal end adapted to be introduced into the common carotid artery, aproximal end, and a lumen extending between the distal and proximalends; a proximal extension having a distal end, a proximal end, and alumen therebetween, wherein the distal end of the proximal extension isconnected to the proximal end of the sheath at a junction so that thelumens of each are contiguous; a flow line having a lumen, said flowline connected near the junction so that blood flowing into the distalend of the sheath can flow into the lumen of the flow line; and ahemostasis valve at the proximal end of the proximal extension, saidhemostasis valve being adapted to inhibit blood flow from the proximalextension while allowing catheter introduction through the proximalextension and into the distal sheath.

In another aspect, there is disclosed a method for accessing andtreating a carotid artery. The method comprises forming a penetration ina wall of a common carotid artery; positioning an access sheath throughthe penetration; blocking blood flow from the common carotid artery pastthe sheath; allowing retrograde blood flow from the carotid artery intothe sheath and from the sheath via a flow path to a return site; andmodifying blood flow through the flow path based on feedback data.

In another aspect, there is disclosed a method for accessing andtreating a carotid artery. The method comprises forming a penetration ina wall of a common carotid artery; positioning an access sheath throughthe penetration; blocking blood flow from the common carotid artery pastthe sheath; allowing retrograde blood flow from the carotid artery intothe sheath and from the sheath via a flow path to a return site; andmonitoring flow through the flow path.

In another aspect, there is disclosed a method for accessing andtreating a carotid artery. The method comprises: forming a penetrationin a wall of a common carotid artery; positioning an arterial accesssheath through the penetration; blocking blood flow from the commoncarotid artery past the sheath; allowing retrograde blood flow from theinternal carotid artery into the sheath while the common carotid arteryremains blocked; and adjusting the state of retrograde blood flowthrough the sheath.

In another aspect, there is disclosed a method for accessing andtreating a carotid artery. The method comprises forming a penetration ina wall of a common carotid artery; positioning an arterial access sheaththrough the penetration; blocking blood flow from the common carotidartery past the sheath; allowing retrograde blood flow from the internalcarotid artery into the sheath while the common carotid artery remainsblocked; and adjusting a rate of retrograde blood flow from the sheathto as high a level as the patient will tolerate, wherein said adjustedrate is a baseline.

This application is related to U.S. Pat. No. 8,157,760 entitled “Methodsand Systems for Establishing Retrograde Carotid Arterial Flow” and U.S.patent application Ser. No. 14/227,585 entitled “Methods and Systems ForEstablishing Retrograde Carotid Arterial Blood Flow”, both of which areincorporated herein by reference.

FIG. 1A shows a first embodiment of a retrograde flow system 100 that isadapted to establish and facilitate retrograde or reverse flow bloodcirculation in the region of the carotid artery bifurcation in order tolimit or prevent the release of emboli into the cerebral vasculature,particularly into the internal carotid artery. The system 100 interactswith the carotid artery to provide retrograde flow from the carotidartery to a venous return site, such as the internal jugular vein (or toanother return site such as another large vein or an external receptaclein alternate embodiments.) The retrograde flow system 100 includes anarterial access device 110, a venous return device 115, and a shunt 120that provides a passageway for retrograde flow from the arterial accessdevice 110 to the venous return device 115. A flow control assembly 125interacts with the shunt 120. The flow control assembly 125 is adaptedto regulate and/or monitor the retrograde flow from the common carotidartery to the internal jugular vein, as described in more detail below.The flow control assembly 125 interacts with the flow pathway throughthe shunt 120, either external to the flow path, inside the flow path,or both. The arterial access device 110 at least partially inserts intothe common carotid artery CCA and the venous return device 115 at leastpartially inserts into a venous return site such as the internal jugularvein IJV, as described in more detail below. The arterial access device110 and the venous return device 115 couple to the shunt 120 atconnection locations 127 a and 127 b. When flow through the commoncarotid artery is blocked, the natural pressure gradient between theinternal carotid artery and the venous system causes blood to flow in aretrograde or reverse direction RG (FIG. 2A) from the cerebralvasculature through the internal carotid artery and through the shunt120 into the venous system. The flow control assembly 125 modulates,augments, assists, monitors, and/or otherwise regulates the retrogradeblood flow.

In the embodiment of FIG. 1A, the arterial access device 110 accessesthe common carotid artery CCA via a transcarotid approach. Transcarotidaccess provides a short length and non-tortuous pathway from thevascular access point to the target treatment site thereby easing thetime and difficulty of the procedure, compared for example to atransfemoral approach. In an embodiment, the arterial distance from thearteriotomy to the target treatment site (as measured traveling throughthe artery) is 15 cm or less. In an embodiment, the distance is between5 and 10 cm. Additionally, this access route reduces the risk of emboligeneration from navigation of diseased, angulated, or tortuous aorticarch or common carotid artery anatomy. At least a portion of the venousreturn device 115 is placed in the internal jugular vein IJV. In anembodiment, transcarotid access to the common carotid artery is achievedpercutaneously via an incision or puncture in the skin through which thearterial access device 110 is inserted. If an incision is used, then theincision can be about 0.5 cm in length. An occlusion element 129, suchas an expandable balloon, can be used to occlude the common carotidartery CCA at a location proximal of the distal end of the arterialaccess device 110. The occlusion element 129 can be located on thearterial access device 110 or it can be located on a separate device. Inan alternate embodiment, the arterial access device 110 accesses thecommon carotid artery CCA via a direct surgical transcarotid approach.In the surgical approach, the common carotid artery can be occludedusing a tourniquet 2105. The tourniquet 2105 is shown in phantom toindicate that it is a device that is used in the optional surgicalapproach.

In another embodiment, shown in FIG. 1B, the arterial access device 110accesses the common carotid artery CCA via a transcarotid approach whilethe venous return device 115 access a venous return site other than thejugular vein, such as a venous return site comprised of the femoral veinFV. The venous return device 115 can be inserted into a central veinsuch as the femoral vein FV via a percutaneous puncture in the groin.

In another embodiment, shown in FIG. 1C, the arterial access device 110accesses the common carotid artery via a femoral approach. According tothe femoral approach, the arterial access device 110 approaches the CCAvia a percutaneous puncture into the femoral artery FA, such as in thegroin, and up the aortic arch AA into the target common carotid arteryCCA. The venous return device 115 can communicate with the jugular veinJV or the femoral vein FV.

FIG. 1D shows yet another embodiment, wherein the system providesretrograde flow from the carotid artery to an external receptacle 130rather than to a venous return site. The arterial access device 110connects to the receptacle 130 via the shunt 120, which communicateswith the flow control assembly 125. The retrograde flow of blood iscollected in the receptacle 130. If desired, the blood could be filteredand subsequently returned to the patient. The pressure of the receptacle130 could be set at zero pressure (atmospheric pressure) or even lower,causing the blood to flow in a reverse direction from the cerebralvasculature to the receptacle 130. Optionally, to achieve or enhancereverse flow from the internal carotid artery, flow from the externalcarotid artery can be blocked, typically by deploying a balloon or otherocclusion element in the external carotid artery just above thebifurcation with the internal carotid artery. FIG. 1D shows the arterialaccess device 110 arranged in a transcarotid approach with the CCAalthough it should be appreciated that the use of the externalreceptacle 130 can also be used with the arterial access device 110 in atransfemoral approach.

With reference to the enlarged view of the carotid artery in FIG. 2A, aninterventional device, such as a stent delivery system 135 or otherworking catheter, can be introduced into the carotid artery via thearterial access device 110, as described in detail below. The stentdelivery system 135 can be used to treat the plaque P such as to deploya stent into the carotid artery. The arrow RG in FIG. 2A represents thedirection of retrograde flow.

FIG. 2B shows another embodiment, wherein the arterial access device 110is used for the purpose of creating an arterial-to-venous shunt as wellas introduction of at least one interventional device into the carotidartery. A separate arterial occlusion device 112 with an occlusionelement 129 can be used to occlude the common carotid artery CCA at alocation proximal to the distal end of the arterial access device 110.

FIG. 2C shows yet another embodiment wherein the arterial access device110 is used for the purpose of creating an arterial-to-venous shunt aswell as arterial occlusion using an occlusion element 129. A separatearterial introducer device can be used for the introduction of at leastone interventional device into the carotid artery at a location distalto the arterial access device 110.

Description of Anatomy

Collateral Brain Circulation

The Circle of Willis CW is the main arterial anastomatic trunk of thebrain where all major arteries which supply the brain, namely the twointernal carotid arteries (ICAs) and the vertebral basilar system,connect. The blood is carried from the Circle of Willis by the anterior,middle and posterior cerebral arteries to the brain. This communicationbetween arteries makes collateral circulation through the brainpossible. Blood flow through alternate routes is made possible therebyproviding a safety mechanism in case of blockage to one or more vesselsproviding blood to the brain. The brain can continue receiving adequateblood supply in most instances even when there is a blockage somewherein the arterial system (e.g., when the ICA is ligated as describedherein). Flow through the Circle of Willis ensures adequate cerebralblood flow by numerous pathways that redistribute blood to the deprivedside.

The collateral potential of the Circle of Willis is believed to bedependent on the presence and size of its component vessels. It shouldbe appreciated that considerable anatomic variation between individualscan exist in these vessels and that many of the involved vessels may bediseased. For example, some people lack one of the communicatingarteries. If a blockage develops in such people, collateral circulationis compromised resulting in an ischemic event and potentially braindamage. In addition, an autoregulatory response to decreased perfusionpressure can include enlargement of the collateral arteries, such as thecommunicating arteries, in the Circle of Willis. An adjustment time isoccasionally required for this compensation mechanism before collateralcirculation can reach a level that supports normal function. Thisautoregulatory response can occur over the space of 15 to 30 seconds andcan only compensate within a certain range of pressure and flow drop.Thus, it is possible for a transient ischemic attack to occur during theadjustment period. Very high retrograde flow rate for an extended periodof time can lead to conditions where the patient's brain is not gettingenough blood flow, leading to patient intolerance as exhibited byneurologic symptoms or in some cases a transient ischemic attack.

FIG. 4 depicts a normal cerebral circulation and formation of Circle ofWillis CW. The aorta AO gives rise to the brachiocephalic artery BCA,which branches into the left common carotid artery LCCA and leftsubclavian artery LSCA. The aorta AO further gives rise to the rightcommon carotid artery RCCA and right subclavian artery RSCA. The leftand right common carotid arteries CCA gives rise to internal carotidarteries ICA which branch into the middle cerebral arteries MCA,posterior communicating artery PcoA, and anterior cerebral artery ACA.The anterior cerebral arteries ACA deliver blood to some parts of thefrontal lobe and the corpus striatum. The middle cerebral arteries MCAare large arteries that have tree-like branches that bring blood to theentire lateral aspect of each hemisphere of the brain. The left andright posterior cerebral arteries PCA arise from the basilar artery BAand deliver blood to the posterior portion of the brain (the occipitallobe).

Anteriorly, the Circle of Willis is formed by the anterior cerebralarteries ACA and the anterior communicating artery ACoA which connectsthe two ACAs. The two posterior communicating arteries PCoA connect theCircle of Willis to the two posterior cerebral arteries PCA, whichbranch from the basilar artery BA and complete the Circle posteriorly.

The common carotid artery CCA also gives rise to external carotid arteryECA, which branches extensively to supply most of the structures of thehead except the brain and the contents of the orbit. The ECA also helpssupply structures in the neck and face.

Carotid Artery Bifurcation

FIG. 5 shows an enlarged view of the relevant vasculature in thepatient's neck. The common carotid artery CCA branches at bifurcation Binto the internal carotid artery ICA and the external carotid arteryECA. The bifurcation is located at approximately the level of the fourthcervical vertebra. FIG. 5 shows plaque P formed at the bifurcation B.

As discussed above, the arterial access device 110 can access the commoncarotid artery CCA via a transcarotid approach. Pursuant to thetranscarotid approach, the arterial access device 110 is inserted intothe common carotid artery CCA at an arterial access location L, whichcan be, for example, a surgical incision or puncture in the wall of thecommon carotid artery CCA. There is typically a distance D of around 5to 7 cm between the arterial access location L and the bifurcation B.When the arterial access device 110 is inserted into the common carotidartery CCA, it is undesirable for the distal tip of the arterial accessdevice 110 to contact the bifurcation B as this could disrupt the plaqueP and cause generation of embolic particles. In order to minimize thelikelihood of the arterial access device 110 contacting the bifurcationB, in an embodiment only about 2-4 cm of the distal region of thearterial access device is inserted into the common carotid artery CCAduring a procedure.

The common carotid arteries are encased on each side in a layer offascia called the carotid sheath. This sheath also envelops the internaljugular vein and the vagus nerve. Anterior to the sheath is thesternocleidomastoid muscle. Transcarotid access to the common carotidartery and internal jugular vein, either percutaneous or surgical, canbe made immediately superior to the clavicle, between the two heads ofthe sternocleidomastoid muscle and through the carotid sheath, with caretaken to avoid the vagus nerve.

At the upper end of this sheath, the common carotid artery bifurcatesinto the internal and external carotid arteries. The internal carotidartery continues upward without branching until it enters the skull tosupply blood to the retina and brain. The external carotid arterybranches to supply blood to the scalp, facial, ocular, and othersuperficial structures. Intertwined both anterior and posterior to thearteries are several facial and cranial nerves. Additional neck musclesmay also overlay the bifurcation. These nerve and muscle structures canbe dissected and pushed aside to access the carotid bifurcation during acarotid endarterectomy procedure. In some cases the carotid bifurcationis closer to the level of the mandible, where access is more challengingand with less room available to separate it from the various nerveswhich should be spared. In these instances, the risk of inadvertentnerve injury can increase and an open endarterectomy procedure may notbe a good option.

Detailed Description of Retrograde Blood Flow System

As discussed, the retrograde flow system 100 includes the arterialaccess device 110, venous return device 115, and shunt 120 whichprovides a passageway for retrograde flow from the arterial accessdevice 110 to the venous return device 115. The system also includes theflow control assembly 125, which interacts with the shunt 120 toregulate and/or monitor retrograde blood flow through the shunt 120.Exemplary embodiments of the components of the retrograde flow system100 are now described.

Arterial Access Device

FIG. 6A shows an exemplary embodiment of the arterial access device 110,which comprises a distal sheath 605, a proximal extension 610, a flowline 615, an adaptor or Y-connector 620, and a hemostasis valve 625. Thearterial access device may also comprise a dilator 645 with a taperedtip 650 and an introducer guide wire 611. The arterial access devicetogether with the dilator and introducer guidewire are used together togain access to a vessel. Features of the arterial access device may beoptimized for transcarotid access. For example, the design of the accessdevice components may be optimized to limit the potential injury on thevessel due to a sharp angle of insertion, allow atraumatic and securesheath insertion, and limiting the length of sheath, sheath dilator, andintroducer guide wire inserted into the vessel.

The distal sheath 605 is adapted to be introduced through an incision orpuncture in a wall of a common carotid artery, either an open surgicalincision or a percutaneous puncture established, for example, using theSeldinger technique. The length of the sheath can be in the range from 5to 15 cm, usually being from 10 cm to 12 cm. The inner diameter istypically in the range from 7 Fr (1 Fr=0.33 mm), to 10 Fr, usually being8 Fr. Particularly when the sheath is being introduced through thetranscarotid approach, above the clavicle but below the carotidbifurcation, it is desirable that the sheath 605 be highly flexiblewhile retaining hoop strength to resist kinking and buckling. Thus, thedistal sheath 605 can be circumferentially reinforced, such as by braid,helical ribbon, helical wire, cut tubing, or the like and have an innerliner so that the reinforcement structure is sandwiched between an outerjacket layer and the inner liner. The inner liner may be a low frictionmaterial such as PTFE. The outer jacket may be one or more of a group ofmaterials including Pebax, thermoplastic polyurethane, or nylon. In anembodiment, the reinforcement structure or material and/or outer jacketmaterial or thickness may change over the length of the sheath 605 tovary the flexibility along the length. In an alternate embodiment, thedistal sheath is adapted to be introduced through a percutaneouspuncture into the femoral artery, such as in the groin, and up theaortic arch AA into the target common carotid artery CCA.

The distal sheath 605 can have a stepped or other configuration having areduced diameter distal region 630, as shown in FIG. 6B, which shows anenlarged view of the distal region 630 of the sheath 605. The distalregion 630 of the sheath can be sized for insertion into the carotidartery, typically having an inner diameter in the range from 2.16 mm(0.085 inch) to 2.92 mm (0.115 inch) with the remaining proximal regionof the sheath having larger outside and luminal diameters, with theinner diameter typically being in the range from 2.794 mm (0.110 inch)to 3.43 mm (0.135 inch). The larger luminal diameter of the proximalregion minimizes the overall flow resistance of the sheath. In anembodiment, the reduced-diameter distal section 630 has a length ofapproximately 2 cm to 4 cm. The relatively short length of thereduced-diameter distal section 630 permits this section to bepositioned in the common carotid artery CCA via the transcarotidapproach with reduced risk that the distal end of the sheath 605 willcontact the bifurcation B. Moreover, the reduced diameter section 630also permits a reduction in size of the arteriotomy for introducing thesheath 605 into the artery while having a minimal impact in the level offlow resistance. Further, the reduced distal diameter section may bemore flexible and thus more conformal to the lumen of the vessel.

With reference again to FIG. 6A, the proximal extension 610, which is anelongated body, has an inner lumen which is contiguous with an innerlumen of the sheath 605. The lumens can be joined by the Y-connector 620which also connects a lumen of the flow line 615 to the sheath. In theassembled system, the flow line 615 connects to and forms a first leg ofthe retrograde shunt 120 (FIG. 1). The proximal extension 610 can have alength sufficient to space the hemostasis valve 625 well away from theY-connector 620, which is adjacent to the percutaneous or surgicalinsertion site. By spacing the hemostasis valve 625 away from apercutaneous insertion site, the physician can introduce a stentdelivery system or other working catheter into the proximal extension610 and sheath 605 while staying out of the fluoroscopic field whenfluoroscopy is being performed. In an embodiment, the proximal extensionis about 16.9 cm from a distal most junction (such as at the hemostasisvalve) with the sheath 605 to the proximal end of the proximalextension. In an embodiment, the proximal extension has an innerdiameter of 0.125 inch and an outer diameter of 0.175 inch. In anembodiment, the proximal extension has a wall thickness of 0.025 inch.The inner diameter may range, for example, from 0.60 inch to 0.150 inchwith a wall thickness of 0.010 inch to 0.050 inch. In anotherembodiment, the inner diameter may range, for example, from 0.150 inchto 0.250 inch with a wall thickness of 0.025 inch to 0.100 inch. Thedimensions of the proximal extension may vary. In an embodiment, theproximal extension has a length within the range of about 12-20 cm. Inanother embodiment, the proximal extension has a length within the rangeof about 20-30 cm.

In an embodiment, the distance along the sheath from the hemostasisvalve 625 to the distal tip of the sheath 605 is in the range of about25 and 40 cm. In an embodiment, the distance is in the range of about 30and 35 cm. With a system configuration that allows 2.5 cm of sheathintroduction into the artery, and an arterial distance of between 5 and10 cm from the arteriotomy site to the target site, this system enablesa distance in the range of about 32.5 cm to 42.5 cm from the hemostasisvalve 625 (the location of interventional device introduction into theaccess sheath) to the target site of between 32 and 43 cm. This distanceis about a third the distance required in prior art technology.

A flush line 635 can be connected to the side of the hemostasis valve625 and can have a stopcock 640 at its proximal or remote end. Theflush-line 635 allows for the introduction of saline, contrast fluid, orthe like, during the procedures. The flush line 635 can also allowpressure monitoring during the procedure. A dilator 645 having a tapereddistal end 650 can be provided to facilitate introduction of the distalsheath 605 into the common carotid artery. The dilator 645 can beintroduced through the hemostasis valve 625 so that the tapered distalend 650 extends through the distal end of the sheath 605, as best seenin FIG. 7A. The dilator 645 can have a central lumen to accommodate aguide wire. Typically, the guide wire is placed first into the vessel,and the dilator/sheath combination travels over the guide wire as it isbeing introduced into the vessel.

Optionally, a sheath stopper 705 such as in the form of a tube may beprovided which is coaxially received over the exterior of the distalsheath 605, also as seen in FIG. 7A. The sheath stopper 705 isconfigured to act as a sheath stopper to prevent the sheath from beinginserted too far into the vessel. The sheath stopper 705 is sized andshaped to be positioned over the sheath body 605 such that it covers aportion of the sheath body 605 and leaves a distal portion of the sheathbody 605 exposed. The sheath stopper 705 may have a flared proximal end710 that engages the adapter 620, and a distal end 715. Optionally, thedistal end 715 may be beveled, as shown in FIG. 7B. The sheath stopper705 may serve at least two purposes. First, the length of the sheathstopper 705 limits the introduction of the sheath 605 to the exposeddistal portion of the sheath 605, as seen in FIG. 7A, such that thesheath insertion length is limited to the exposed distal portion of thesheath. In an embodiment, the sheath stopper limits the exposed distalportion to a range between 2 and 3 cm. In an embodiment, the sheathstopper limited the exposed distal portion to 2.5 cm. In other words,the sheath stopper may limit insertion of the sheath into the artery toa range between about 2 and 3 cm or to 2.5 cm. Second, the sheathstopper 705 can engage a pre-deployed puncture closure device disposedin the carotid artery wall, if present, to permit the sheath 605 to bewithdrawn without dislodging the closure device. The sheath stopper 705may be manufactured from clear material so that the sheath body may beclearly visible underneath the sheath stopper 705. The sheath stopper705 may also be made from flexible material, or the sheath stopper 705include articulating or sections of increased flexibility so that itallows the sheath to bend as needed in a proper position once insertedinto the artery. The sheath stopper may be plastically bendable suchthat it can be bent into a desired shape such that it retains the shapewhen released by a user. The distal portion of the sheath stopper may bemade from stiffer material, and the proximal portion may be made frommore flexible material. In an embodiment, the stiffer material is 85 Adurometer and the more flexible section is 50 A durometer. In anembodiment, the stiffer distal portion is 1 to 4 cm of the sheathstopper 705. The sheath stopper 705 may be removable from the sheath sothat if the user desired a greater length of sheath insertion, the usercould remove the sheath stopper 705, cut the length (of the sheathstopper) shorter, and re-assemble the sheath stopper 705 onto the sheathsuch that a greater length of insertable sheath length protrudes fromthe sheath stopper 705.

FIG. 7C shows another embodiment of a sheath stopper 705 positionedadjacent a sheath 605 with a dilator 645 positioned therein. The sheathstopper 705 of FIG. 7C may be deformed from a first shaped, such as astraight shape, into a second different from the first shape wherein thesheath stopper retains the second shape until a sufficient externalforce acts on the sheath stopper to change its shape. The second shapemay be for example non-straight, curved, or an otherwise contoured orirregular shape. For example, FIG. 7C shows the sheath stopper 705having multiple bends as well as straight sections. FIG. 7C shows justan example and it should be appreciated that the sheath stopper 705 maybe shaped to have any quantity of bends along its longitudinal axis.FIG. 7D shows the sheath stopper 705 positioned on the sheath 605. Thesheath stopper 705 has a greater stiffness than the sheath 605 such thatthe sheath 605 takes on a shape or contour that conforms to the shape ofcontour of the sheath stopper 705.

The sheath stopper 705 may be shaped according to an angle of the sheathinsertion into the artery and the depth of the artery or body habitus ofthe patient. This feature reduces the force of the sheath tip in theblood vessel wall, especially in cases where the sheath is inserted at asteep angle into the vessel. The sheath stopper may be bent or otherwisedeformed into a shape that assists in orienting the sheath coaxiallywith the artery being entered even if the angle of the entry into thearterial incision is relatively steep. The sheath stopper may be shapedby an operator prior to sheath insertion into the patient. Or, thesheath stopper may be shaped and/or re-shaped in situ after the sheathhas been inserted into the artery. FIGS. 7E and 7F show an example ofthe malleable sheath stopper 705 in use. FIG. 7E shows the sheathstopper 705 positioned on the sheath 605 with the sheath stopper 705 ina straight shape. The sheath 605 takes on the straight shape of thesheath stopper 705 and is entering the artery A at a relatively steepangle such that the distal tip of the sheath 605 abuts or faces the wallof the artery. In FIG. 7F, a user has bent the sheath stopper 705 so asto adjust the angle of entry of the sheath 605 so that the longitudinalaxis of the sheath 605 is more aligned with the axis of the artery A. Inthis manner, the sheath stopper 705 has been formed by a user into ashape that assists in directing the sheath 605 away from the opposingwall of the artery A and into a direction that is more coaxial with theaxis of the artery A relative to the shape in FIG. 7E.

In an embodiment, the sheath stopper 705 is made from malleablematerial, or with an integral malleable component positioned on or inthe sheath stopper. In another embodiment, the sheath stopper isconstructed to be articulated using an actuator such as concentrictubes, pull wires, or the like. The wall of the sheath stopper may bereinforced with a ductile wire or ribbon to assist it in holding itsshape against external forces such as when the sheath stopper encountersan arterial or entryway bend. Or the sheath stopper may be constructedof a homogeneous malleable tube material, including metal and polymer.The sheath stopper body may also be at least partially constructed of areinforced braid or coil capable of retaining its shape afterdeformation.

Another sheath stopper embodiment is configured to facilitate adjustmentof the sheath stopper position (relative to the sheath) even after thesheath is positioned in the vessel. One embodiment of the sheath stopperincludes a tube with a slit along most or all of the length, so that thesheath stopper can be peeled away from the sheath body, moved forward orbackwards as desired, and then re-positioned along the length of thesheath body. The tube may have a tab or feature on the proximal end soit may be grasped and more easily to peel away.

In another embodiment, the sheath stopper is a very short tube (such asa band), or ring that resides on the distal section of the sheath body.The sheath stopper may include a feature that could be grasped easily byforceps, for example, and pulled back or forwards into a new position asdesired to set the sheath insertion length to be appropriate for theprocedure. The sheath stopper may be fixed to the sheath body througheither friction from the tube material, or a clamp that can be opened orclosed against the sheath body. The clamp may be a spring-loaded clampthat is normally clamped onto the sheath body. To move the sheathstopper, the user may open the clamp with his or her fingers or aninstrument, adjust the position of the clamp, and then release theclamp. The clamp is designed not to interfere with the body of thesheath.

In another embodiment, the sheath stopper includes a feature that allowssuturing the sheath stopper and sheath to the tissue of the patient, toimprove securement of the sheath and reduce risk of sheath dislodgement.The feature may be suture eyelets that are attached or molded into thesheath stopper tube.

In another embodiment, as shown in FIG. 9A, the sheath stopper 705includes a distal flange 710 sized and shaped to distribute the force ofthe sheath stopper over a larger area on the vessel wall and therebyreduce the risk of vessel injury or accidental insertion of the sheathstopper through the arteriotomy and into the vessel. The flange 710 mayhave a rounded shape or other atraumatic shape that is sufficientlylarge to distribute the force of the sheath stopper over a large area onthe vessel wall. In an embodiment, the flange is inflatable ormechanically expandable. For example, the arterial sheath and sheathstopper may be inserted through a small puncture in the skin into thesurgical area, and then expanded prior to insertion of the sheath intothe artery.

The sheath stopper may include one or more cutouts or indents 720 alongthe length of the sheath stopper which are patterned in a staggeredconfiguration such that the indents increase the bendability of thesheath stopper while maintaining axial strength to allow forward forceof the sheath stopper against the arterial wall. The indents may also beused to facilitate securement of the sheath to the patient via sutures,to mitigate against sheath dislodgement. The sheath stopper may alsoinclude a connector element 730 on the proximal end which corresponds tofeatures on the arterial sheath such that the sheath stopper can belocked or unlocked from the arterial sheath. For example, the connectorelement is a hub with generally L-shaped slots 740 that correspond topins 750 on the hub to create a bayonet mount-style connection. In thismanner, the sheath stopper can be securely attached to the hub to reducethe likelihood that the sheath stopper will be inadvertently removedfrom the hub unless it is unlocked from the hub.

The distal sheath 605 can be configured to establish a curved transitionfrom a generally anterior-posterior approach over the common carotidartery to a generally axial luminal direction within the common carotidartery. Arterial access through the common carotid arterial wall eitherfrom a direct surgical cut down or a percutaneous access may require anangle of access that is typically larger than other sites of arterialaccess. This is due to the fact that the common carotid insertion siteis much closer to the treatment site (i.e., carotid bifurcation) thanfrom other access points. A larger access angle is needed to increasethe distance from the insertion site to the treatment site to allow thesheath to be inserted at an adequate distance without the sheath distaltip reaching the carotid bifurcation. For example, the sheath insertionangle is typically 30-45 degrees or even larger via a transcarotidaccess, whereas the sheath insertion angle may be 15-20 degrees foraccess into a femoral artery. Thus the sheath must take a greater bendthan is typical with introducer sheaths, without kinking and withoutcausing undue force on the opposing arterial wall. In addition, thesheath tip desirably does not be abut or contact the arterial wall afterinsertion in a manner that would restrict flow into the sheath. Thesheath insertion angle is defined as the angle between the luminal axisof the artery and the longitudinal axis of the sheath.

The sheath body 605 can be formed in a variety of ways to allow for thisgreater bend required by the angle of access. For example, the sheathand/or the dilator may have a combined flexible bending stiffness lessthan typical introducer sheaths. In an embodiment, the sheath/dilatorcombination (i.e., the sheath with the dilator positioned inside thesheath) has a combined flexible stiffness (E*I) in the range of about 80and 100 N-m²×10⁻⁶, where E is the elastic modulus and I is the areamoment of inertia of the device. The sheath alone may have a bendingstiffness in the range of about 30 to 40 N-m²×10⁻⁶ and the dilator alonehas a bending stiffness in the range of about 40 to 60 N-m²×10⁻⁶.Typical sheath/dilator bending stiffnesses are in the range of 150 to250 N-m²×10⁻⁶. The greater flexibility may be achieved through choice ofmaterials or design of the reinforcement. For example, the sheath mayhave a ribbon coil reinforcement of stainless steel with dimensions0.002″ to 0.003″ thick and 0.005″ to 0.015″ width, and with outer jacketdurometer of between 40 and 55 D. In an embodiment, the coil ribbon is0.003″×0.010″, and the outer jacket durometer is 45 D. In an embodiment,the sheath 605 can be pre-shaped to have a curve or an angle some setdistance from the tip, typically 0.5 to 1 cm. The pre-shaped curve orangle can typically provide for a turn in the range from 5° to 90°,preferably from 10° to 30°. For initial introduction, the sheath 605 canbe straightened with an obturator or other straight or shaped instrumentsuch as the dilator 645 placed into its lumen. After the sheath 605 hasbeen at least partially introduced through the percutaneous or otherarterial wall penetration, the obturator can be withdrawn to allow thesheath 605 to reassume its pre-shaped configuration into the arteriallumen. To retain the curved or angled shape of the sheath body afterhaving been straightened during insertion, the sheath may be heat set inthe angled or curved shape during manufacture. Alternately, thereinforcement structure may be constructed out of nitinol and heatshaped into the curved or angled shape during manufacture. Alternately,an additional spring element may be added to the sheath body, forexample a strip of spring steel or nitinol, with the correct shape,added to the reinforcement layer of the sheath.

Other sheath configurations include having a deflection mechanism suchthat the sheath can be placed and the catheter can be deflected in situto the desired deployment angle. In still other configurations, thecatheter has a non-rigid configuration when placed into the lumen of thecommon carotid artery. Once in place, a pull wire or other stiffeningmechanism can be deployed in order to shape and stiffen the sheath intoits desired configuration. One particular example of such a mechanism iscommonly known as “shape-lock” mechanisms as well described in medicaland patent literature.

Another sheath configuration comprises a curved dilator inserted into astraight but flexible sheath, so that the dilator and sheath are curvedduring insertion. The sheath is flexible enough to conform to theanatomy after dilator removal.

Another sheath embodiment is a sheath that includes one or more flexibledistal sections, such that once inserted and in the angledconfiguration, the sheath is able to bend at a large angle withoutkinking and without causing undue force on the opposing arterial wall.In one embodiment, there is a distalmost section of sheath body 605which is more flexible than the remainder of the sheath body. Forexample, the flexural stiffness of the distalmost section is one half toone tenth the flexural stiffness of the remainder of the sheath body605. In an embodiment, the distalmost section has a flexural stiffnessin the range 30 to 300 N-mm² and the remaining portion of the sheathbody 605 has a flexural stiffness in the range 500 to 1500 N-mm², For asheath configured for a CCA access site, the flexible, distal mostsection comprises a significant portion of the sheath body 222 which maybe expressed as a ratio. In an embodiment, the ratio of length of theflexible, distalmost section to the overall length of the sheath body222 is at least one tenth and at most one half the length of the entiresheath body 222. This change in flexibility may be achieved by variousmethods. For example, the outer jacket may change in durometer and/ormaterial at various sections. Alternately, the reinforcement structureor the materials may change over the length of the sheath body. In anembodiment, the distal-most flexible section ranges from 1 cm to 3 cm.In an embodiment with more than one flexible section, a less flexiblesection (with respect to the distal-most section) may be 1 cm to 2 cmfrom the distal-most proximal section. In an embodiment, the distalflexible section has a bending stiffness in the range of about 30 to 50N-m²×10′ and the less flexible section has a bending stiffness in therange of about 50 and 100 N-m²×10′. In another embodiment, a moreflexible section is located between 0.5 and 1.5 cm for a length ofbetween 1 and 2 cm, to create an articulating section that allows thedistal section of the sheath to align more easily with the vessel axisthough the sheath enters the artery at an angle. These configurationswith variable flexibility sections may be manufactured in severalmanners. For example the reinforced, less flexible section may vary suchthat there is stiffer reinforcement in the proximal section and moreflexible reinforcement in the distal section or in the articulatingsection. In an embodiment, an outer-most jacket material of the sheathis 45 D to 70 D durometer in the proximal section and 80 A to 25 D inthe distalmost section. In an embodiment, the flexibility of the sheathvaries continuously along the length of the sheath body. FIG. 7G showssuch a sheath inserted in the artery, with the flexible distal sectionallowing the sheath body to bend and the distal tip to be in generalalignment with the vessel lumen. In an embodiment, the distal section ismade with a more flexible reinforcement structure, either by varying thepitch of a coil or braid or by incorporating a cut hypotube withdiffering cut patterns. Alternately the distal section has a differentreinforcement structure than the proximal section.

In an embodiment, the distal sheath tapered tip is manufactured fromharder material than the distal sheath body. A purpose of this is tofacilitate ease of sheath insertion by allowing for a very smooth taperon the sheath and reduce the change of sheath tip distortion orovalizing during and after sheath insertion into the vessel. In oneexample the distal tapered tip material is manufactured from a higherdurometer material, for example a 60-72 D shore material. In anotherexample, distal tip is manufactured from a separate material, forexample HDPE, stainless steel, or other suitable polymers or metals. Inan additional embodiment, the distal tip is manufactured from radiopaquematerial, either as an additive to the polymer material, for exampletungsten or barium sulfate, or as an inherent property of the material(as is the case with most metal materials).

In another embodiment, the dilator 645 may also have variable stiffness.For example the tapered tip 650 of the dilator may be made from moreflexible material than the proximal portion of the dilator, to minimizethe risk of vessel injury when the sheath and dilator are inserted intothe artery. In an embodiment, the distal flexible section has a bendingstiffness in the range of about 45 to 55 N-m²×10⁻⁶ and a less flexibleproximal section has a bending stiffness in the range of about 60 and 90N-m²×10⁻⁶. The taper shape of the dilator may also be optimized fortranscarotid access. For example, to limit the amount of sheath anddilator tip that enter the artery, the taper length and the amount ofthe dilator that extends past the sheath should be shorter than typicalintroducer sheaths. For example, the taper length may be 1 to 1.5 cm,and extend 1.5 to 2 cm from the end of the sheath body. In anembodiment, the dilator contains a radiopaque marker at the distal tipso that the tip position is easily visible under fluoroscopy.

In another embodiment, the introducer guide wire is optimally configuredfor transcarotid access. Typically when inserting an introducer sheathinto a vessel, an introducer guide wire is first inserted into thevessel. This may be done either with a micropuncture technique or amodified Seldinger technique. Usually there is a long length of vesselin the direction that the sheath is to be inserted into which anintroducer guidewire may be inserted, for example into the femoralartery. In this instance, a user may introduce a guide wire between 10and 15 cm or more into the vessel before inserting the sheath. The guidewire is designed to have a flexible distal section so as not to injurethe vessel when being introduced into the artery. The flexible sectionof an introducer sheath guide wire is typically 5 to 6 cm in length,with a gradual transition to the stiffer section. Inserting the guidewire 10 to 15 cm means the stiffer section of the guide wire ispositioned in the area of the puncture and allows a stable support forsubsequent insertion of the sheath and dilator into the vessel. However,in the case of transcarotid sheath insertion into the common carotidartery, there is a limit on how much guide wire may be inserted into thecarotid artery. In cases with carotid artery disease at the bifurcationor in the internal carotid artery, it is desirable to minimize the riskof emboli by inserting the wire into the external carotid artery (ECA),which would mean only about 5 to 7 cm of guide wire insertion, or tostop it before it reaches the bifurcation, which would be only 3 to 5 cmof guide wire insertion. Thus, a transcarotid sheath guidewire may havea distal flexible section of between 3 and 4 cm, and/or a shortertransition to a stiffer section. Alternately, a transcarotid sheathguidewire has an atraumatic tip section but have a very distal and shorttransition to a stiffer section. For example, the soft tip section is1.5 to 2.5 cm, followed by a transition section with length from 3 to 5cm, followed by a stiffer proximal segment, with the stiffer proximalsection comprising the remainder of the wire.

In addition to the configurations described above, features may beincluded in the introducer guide wire, or the micropuncture catheter, orthe micropuncture catheter guide wire, to prevent inadvertentadvancement of these devices into the diseased portion of the carotidartery. For example a stopper feature may be positioned over theintroducer guide wire, micropuncture catheter and/or the micropunctureguide wire to limit the length these devices can be inserted. Thestopper feature may be, for example, a short section of tubing which canbe slideably positioned on the device, and once positioned remains inplace on the device via friction. For example, the stopper feature maybe manufactured from soft polymer material such as silicone rubber,polyurethane, or other thermoplastic elastomer. The stopper feature mayhave an inner diameter the same size or even slightly smaller than thedevice diameter. Alternately the stopper feature may be configured toclamp on to the device, such that the user must squeeze or otherwiseunlock the stopper feature to unclamp and reposition the device, andthen release or otherwise relock the stopper feature onto the device.The stopper feature may be positioned for optimal entry into the vesselbased on location of the puncture site, distance of the bifurcation withrespect to the puncture site, and amount of disease in the carotidbifurcation.

The sheath guide wire may have guide wire markings to help the userdetermine where the tip of the wire is with respect to the dilator. Forexample, there may be a marking on the proximal end of the wirecorresponding to when the tip of the wire is about to exit the microaccess cannula tip. This marking would provide rapid wire positionfeedback to help the user limit the amount of wire insertion. In anotherembodiment, the wire may include an additional mark to let the user knowthe wire has exited the cannula by a set distance, for example 5 cm.Alternately, the introducer guide wire, micropuncture catheter and/orthe micropuncture guide wire may be constructed or have sectionsconstructed out of material which is markable with a marking pen,wherein the mark is easily visible in a cath lab or operating room (OR)setting. In this embodiment, the user pre-marks the components based onthe anatomic information as described above, and uses these marks todetermine the amount of maximal insertion for each component. Forexample, the guide wires may have a white coating around the section tobe marked.

In an embodiment, the sheath has built-in puncturing capability andatraumatic tip analogous to a guide wire tip. This eliminates the needfor needle and wire exchange currently used for arterial accessaccording to the micropuncture technique, and can thus save time, reduceblood loss, and require less surgeon skill.

In another embodiment, the sheath dilator is configured to be insertedover an 0.018″ guide wire for transcarotid access. Standard sheathinsertion using a micropuncture kit requires first insertion of an0.018″ guide wire through a 22 Ga needle, then exchange of the guidewire to an 0.035″ or 0.038″ guide wire using a micropuncture catheter,and finally insertion of the sheath and dilator over the 0.035″ or0.038″ guide wire. There exist sheaths which are insertable over a0.018″ guidewire, thus eliminating the need for the wire exchange. Thesesheaths, usually labeled “transradial” as they are designed forinsertion into the radial artery, typically have a longer dilator taper,to allow an adequate diameter increase from the 0.018″ wire to the bodyof the sheath. Unfortunately for transcarotid access, the length forsheath and dilator insertion is limited and therefore these existingsheaths are not appropriate. Another disadvantage is that the 0.018″guide wire may not have the support needed to insert a sheath with asharper angle into the carotid artery. In the embodiment disclosed here,a transcarotid sheath system includes a sheath body, a sheath dilator,and an inner tube with a tapered distal edge that slidably fits insidethe sheath dilator and can accommodate an 0.018″ guide wire.

To use this sheath system embodiment, the 0.018″ guide wire is firstinserted into the vessel through a 22 Ga needle. The sheath system whichis coaxially assembled is inserted over the 0.018″ wire. The inner tubeis first advanced over the 0.018″ wire which essentially transforms itinto the equivalent of an 0.035″ or 0.038″ guide wire in both outerdiameter and mechanical support. It is locked down to the 0.018″ wire onthe proximal end. The sheath and dilator are then advanced over the0.018″ wire and inner tube into the vessel. This configurationeliminates the wire exchange step without the need for a longer dilatortaper as with current transradial sheaths and with the same guide wiresupport as standard introducer sheaths. As described above, thisconfiguration of sheath system may include stopper features whichprevent inadvertent advancement too far of the 0.018″ guide wire and/orinner tube during sheath insertion. Once the sheath is inserted, thedilator, inner tube, and 0.018″ guide wire are removed.

FIG. 8A shows another embodiment of the arterial access device 110. Thisembodiment is substantially the same as the embodiment shown in FIG. 6A,except that the distal sheath 605 includes an occlusion element 129 foroccluding flow through, for example the common carotid artery. If theoccluding element 129 is an inflatable structure such as a balloon orthe like, the sheath 605 can include an inflation lumen thatcommunicates with the occlusion element 129. The occlusion element 129can be an inflatable balloon, but it could also be an inflatable cuff, aconical or other circumferential element which flares outwardly toengage the interior wall of the common carotid artery to block flowtherepast, a membrane-covered braid, a slotted tube that radiallyenlarges when axially compressed, or similar structure which can bedeployed by mechanical means, or the like. In the case of balloonocclusion, the balloon can be compliant, non-compliant, elastomeric,reinforced, or have a variety of other characteristics. In anembodiment, the balloon is an elastomeric balloon which is closelyreceived over the exterior of the distal end of the sheath prior toinflation. When inflated, the elastomeric balloon can expand and conformto the inner wall of the common carotid artery. In an embodiment, theelastomeric balloon is able to expand to a diameter at least twice thatof the non-deployed configuration, frequently being able to be deployedto a diameter at least three times that of the undeployed configuration,more preferably being at least four times that of the undeployedconfiguration, or larger.

As shown in FIG. 8B, the distal sheath 605 with the occlusion element129 can have a stepped or other configuration having a reduced diameterdistal region 630. The distal region 630 can be sized for insertion intothe carotid artery with the remaining proximal region of the sheath 605having larger outside and luminal diameters, with the inner diametertypically being in the range from 2.794 mm (0.110 inch) to 3.43 mm(0.135 inch). The larger luminal diameter of the proximal regionminimizes the overall flow resistance of the sheath. In an embodiment,the reduced-diameter distal section 630 has a length of approximately 2cm to 4 cm. The relatively short length of the reduced-diameter distalsection 630 permits this section to be positioned in the common carotidartery CCA via the transcarotid approach with reduced risk that thedistal end of the sheath 605 will contact the bifurcation B.

FIG. 2B shows an alternative embodiment, wherein the occlusion element129 can be introduced into the carotid artery on a second sheath 112separate from the distal sheath 605 of the arterial access device 110.The second or “proximal” sheath 112 can be adapted for insertion intothe common carotid artery in a proximal or “downward” direction awayfrom the cerebral vasculature. The second, proximal sheath can includean inflatable balloon 129 or other occlusion element, generally asdescribed above. The distal sheath 605 of the arterial access device 110can be then placed into the common carotid artery distal of the second,proximal sheath and generally oriented in a distal direction toward thecerebral vasculature. By using separate occlusion and access sheaths,the size of the arteriotomy needed for introducing the access sheath canbe reduced.

FIG. 2C shows yet another embodiment of a two arterial sheath system,wherein the interventional devices are introduced via an introducersheath 114 separate from the distal sheath 605 of the arterial device110. A second or “distal” sheath 114 can be adapted for insertion intothe common carotid artery distal to the arterial access device 110. Aswith the previous embodiment, the use of two separate access sheathsallows the size of each arteriotomy to be reduced.

In a situation with a sharp sheath insertion angle and/or a short lengthof sheath inserted in the artery, such as one might see in atranscarotid access procedure, the distal tip of the sheath has a higherlikelihood of being partially or totally positioned against the vesselwall, thereby restricting flow into the sheath. In an embodiment, thesheath is configured to center the tip in the lumen of the vessel. Onesuch embodiment includes a balloon such as the occlusion element 129described above. In another embodiment, a balloon may not be occlusiveto flow but still center the tip of the sheath away from a vessel wall,like an inflatable bumper. In another embodiment, expandable featuresare situated at the tip of the sheath and mechanically expanded once thesheath is in place. Examples of mechanically expandable features includebraided structures or helical structures or longitudinal struts whichexpand radially when shortened.

In an embodiment, occlusion of the vessel proximal to the distal tip ofthe sheath may be done from the outside of the vessel, as in a Rummeltourniquet or vessel loop proximal to sheath insertion site. In analternate embodiment, an occlusion device may fit externally to thevessel around the sheath tip, for example an elastic loop, inflatablecuff, or a mechanical clamp that could be tightened around the vesseland distal sheath tip. In a system of flow reversal, this method ofvessel occlusion minimizes the area of static blood flow, therebyreducing risk of thrombus formation, and also ensure that the sheath tipis axially aligned with vessel and not partially or fully blocked by thevessel wall.

Another arterial access device is shown in FIGS. 9A-9D. Thisconfiguration has a different style of connection to the flow shunt thanthe versions described previously. FIG. 9A shows the components of thearterial access device 110 including arterial access sheath 605, sheathdilator 645, sheath stopper 705, and sheath guidewire 611. FIG. 9B showsthe arterial access device 110 as it would be assembled for insertionover the sheath guide wire 611 into the carotid artery. After the sheathis inserted into the artery and during the procedure, the sheath guidewire 611 and sheath dilator 705 are removed. In this configuration, thesheath has a sheath body 605, proximal extension 610, and proximalhemostasis valve 625 with flush line 635 and stopcock 640. The proximalextension 610 extends from a Y-adapter 660 to the hemostasis valve 625where the flush line 635 is connected. The sheath body 605 is theportion that is sized to be inserted into the carotid artery and isactually inserted into the artery during use.

Instead of a Y-connector with a flow line connection terminating in avalve, the sheath has a Y-adaptor 660 that connects the distal portionof the sheath to the proximal extension 610. The Y-adapter can alsoinclude a valve 670 that can be operated to open and close fluidconnection to a connector or hub 680 that can be removably connected toa flow line such as a shunt. The valve 670 is positioned immediatelyadjacent to an internal lumen of the adapter 660, which communicateswith the internal lumen of the sheath body 605. FIGS. 9C and 9D showdetails in cross section of the Y-adaptor 660 with the valve 670 and thehub 680. FIG. 9C shows the valve closed to the connector. This is theposition that the valve would be in during prep of the arterial sheath.The valve is configured so that there is no potential for trapped airduring prep of the sheath. FIG. 9D shows the valve open to theconnector. This position would be used once the flow shunt 120 isconnected to hub 680, and would allow blood flow from the arterialsheath into the shunt. This configuration eliminates the need to prepboth a flush line and flow line, instead allowing prep from the singleflush line 635 and stopcock 640. This single-point prep is identical toprep of conventional introducer sheaths which do not have connections toshunt lines, and is therefore more familiar and convenient to the user.In addition, the lack of flow line on the sheath makes handling of thearterial sheath easier during prep and insertion into the artery.

With reference again to FIG. 9A, the sheath may also contain a secondmore distal connector 690, which is separated from the Y-adaptor 660 bya segment of tubing 665. A purpose of this second connector and thetubing 665 is to allow the valve 670 to be positioned further proximalfrom the distal tip of the sheath, while still limiting the length ofthe insertable portion of the sheath 605, and therefore allow a reducedlevel of exposure of the user to the radiation source as the flow shuntis connected to the arterial sheath during the procedure. In anembodiment, the distal connector 690 contains suture eyelets to aid insecurement of the sheath to the patient once positioned.

During a transcarotid artery revascularization (TCAR) procedure, thearterial sheath 605 can be inserted into the common carotid artery (CCA)of the patient. As described elsewhere herein, to achieve reverse flowof blood, the CCA may be occluded to stop antegrade blood flow from theaorta through the CCA. Flow through the CCA can be occluded with anexternal vessel loop or tape, a vascular clamp, an internal occlusionmember such as a balloon, or other type of occlusion means. When flowthrough CCA is blocked, the natural pressure gradient between theinternal carotid artery (ICA) and the venous system will cause blood toflow in a retrograde or reverse direction from the cerebral vasculature.Blood from the ICA and the external carotid artery (ECA) flows in aretrograde direction and the systems described herein allow theretrograde blood to flow into the sheath 605, through the flowcontroller 1130, the venous sheath 910, and then returned into thepatient's femoral vein as described elsewhere herein. Loose embolicmaterial can be carried with the retrograde blood flow into the arterialsheath 605.

FIGS. 13A-13B illustrate an arterial sheath 605 inserted within a vesselV, such as the carotid artery, exposed through an incision I. A sheathguidewire 611 and an arterial access sheath dilator 645 protrude outfrom a distal opening 641 near the distal region 630 of the sheath 605.A sheath stopper 705 can be used with the sheath 605, as describedelsewhere herein. Manual occlusion of the vessel V by a clinician at anocclusion location proximal to the distal tip of the sheath 605 may beprovided from the outside of the vessel V using a vascular clamp 800,such as a Rummel tourniquet or vessel loop positioned proximal to thesheath insertion site. An occlusion device may fit externally to thevessel V around the sheath tip, for example, an elastic loop, inflatablecuff, or a mechanical clamp that can be tightened around the vessel andthe distal sheath tip. In a flow reversal system, this type of vesselocclusion can minimize creation of a zone of static blood flow, therebyreducing the risk of thrombus formation. This also ensures that thesheath tip is axially aligned with the vessel V and avoids partially orfully blocking the distal opening 641 by the vessel wall.

Despite these clamp techniques, the zone of static blood flow can stillbe created. FIG. 13B illustrates a system for retrograde blood flow intothe distal opening 641 of the arterial sheath 605 after removal of theaccess sheath dilator 645. The location of the vascular clamp 800 inFIG. 13B is partially obscured by the presence of the sheath stopper705. Embolic material within the retrograde blood flow may drift and betrapped within a zone 905 of static blood flow within the vessel Vbetween the distal opening 641 of the arterial sheath 605 and thelocation of the vascular clamp 800 proximal to the sheath insertionlocation. Embolic material may remain within this zone 905 rather thanflow into the distal opening 641 of the arterial sheath 605. Once thetarget vessel has been treated by the operator, the vascular clamp 800is released permitting resumption of antegrade blood flow. Embolicmaterial from this zone 905 may be carried into the neurovasculaturewhen the vascular clamp 800 is released and antegrade blood flowresumes. The trapped embolic material within the zone 905 may cause anischemic event despite the use of reverse flow embolic protection duringthe procedure because it fails to ever enter the lumen of the arterialsheath 605 during the period of retrograde flow.

FIG. 13C illustrates a distal end region of an implementation of anarterial sheath 605 having a fenestrated distal portion 643. Thefenestrated distal portion 643 of the sheath 605 includes one or moreside holes or fenestrations 646 in the side wall of the sheath 605. Asdescribed above, blood from zone 905 may potentially contain embolicmaterial that would otherwise flow into the neurovasculature uponrelease of the vascular clamp 800. Material from this zone 905 can enterthe sheath 605 through the fenestrations 646 in the sidewall of thesheath 605. The fenestrations 646 can also maintain flow into the sheath605 even if the distal opening 641 at the distal tip of sheath 605 ispartially or fully blocked by arterial wall. Blood and any embolicmaterial can flow into the lumen of the sheath 604 through the one ormore fenestrations 646 and transported proximally through the embolicprotection system with the retrograde blood flow.

The location, distribution, shape, and size of the fenestrations 646 canvary. The fenestrations 646 can be distributed longitudinally and/orcircumferentially along the distal portion 643 of the arterial sheath605. The location and distribution of the fenestrations 646 can beselected based on whether a sheath stopper 705 is to be used with thesheath 605. For example, a sheath stopper 705 can be positioned on thearterial sheath 605 to limit an insertion depth of the sheath 605 intothe vessel. In some implementations, the sheath stopper 705 limits theinsertion depth to 2.5 cm. Thus, the one or more fenestrations 646 canbe distributed along the distal-most 2.5 cm of the sheath 605.Fenestrations 646 may also be distributed along the sheath 605 over agreater distance. The proximal sheath fenestrations 646 sitting externalto the vessel can be blocked by a sleeve or other feature of the systemthereby preventing leakage.

As described elsewhere herein, the sheath 605 can be reinforced toprovide improved flexibility and kink-resistance. The reinforcement canbe a spiral-wound stainless steel ribbon, braid, or mesh as is known inthe art. The one or more fenestrations 646 can be positioned such thatthey extend through and/or align with the side wall in the space(s)between the reinforcement material such that the fenestrations 646 andthe space(s) collectively form passageways through which fluid can flowinto the internal lumen of the sheath 605. The spaces within thereinforcement layer can include gaps between individual coils, circularor diamond-shaped holes through the braid or mesh, etc. Thefenestrations 646 through the sidewall of the sheath 605 align withthese spaces or gaps in the reinforcement layer thereby providingadditional entrance points for blood and embolic material whilemaintaining the structural benefits of the reinforcement layer. Theorientation of the fenestrations 646 can be such that they align withthese spaces between the reinforcement material (see FIG. 13D). Thefenestrations 646 can vary in their number, size, and shape, includingcircular, oval, rectangular, or other elongate shape. The elongatefenestrations 646 can extend along an axis perpendicular or at an angleto the longitudinal axis of the sheath overall such that they fit withinor align with the spaces between the reinforcement layer.

For example, as described elsewhere herein the arterial sheath 605 mayhave a ribbon coil reinforcement of stainless steel with dimensions0.002″ to 0.003″ thick and 0.005″ to 0.015″ width. In an embodiment, thecoil ribbon is 0.003″×0.010″. The nominal spacing between thereinforcement coils of the sheath 605 can vary, but generally is about0.020″. The elongated fenestrations 646 can thus have a width of aboutthis size such that they extend through the wall between thereinforcement coils. In some implementations, the fenestrations 646 canbe between about 0.010″ to about 0.080″, with a nominal range of about0.015″-0.020″. Depending on the spacing between the reinforcement, theelongated fenestrations 646 can have a size between 0.015″×0.030″ toabout 0.040″×0.080″. Elongated fenestrations 646 that fit between orwithin the gaps in the reinforcement material can be up to about 0.020″,with a maximum envisioned dimension of about 0.020″×0.080″. It may bepossible to vary the pitch of the coils as well as the width of the coilribbon to adjust and optimize the flexibility and performance of thesheath 605 and the size of the fenestrations 646. For example, thereinforcement material can be a coil ribbon.

The width between the individual coils can be increased near where oneor more fenestrations 646 would extend through the wall of the sheath605. The width near this location can be increased from 0.020″ to0.050″. The fenestrations 646 need not be limited to the location of thegaps in the reinforcement. For example, the reinforcement material canbe a wire or polymer mesh. One or more regions of the mesh can be cut tocreate a larger sized space (while taking into consideration maintainingthe overall functionality of the sheath) and the one or morefenestrations 646 co-located to that larger space.

The embolic protection system can include a passive method of drivingretrograde blood flow into the distal opening 641 at the sheath tip andthe fenestrations 646 in the distal end region 643, for example, byrelying upon arterial-venous pressure differential. The embolicprotection system can also incorporate active aspiration of bloodthrough the arterial sheath 605 to enhance the withdrawal of embolicmaterial into the distal opening 641 as well as through thefenestrations 646. The fenestrations 646 can also be useful indelivering materials into the vessel through the fenestrations 646. Insome implementations, a gentle injection of saline through the lumen ofthe sheath 605 into the vessel through the fenestrations 646 can causeturbulence/agitation within the zone 905 of static blood. The flush offluid can induce any particulates trapped within the zone 905 to bedrawn into the fluid flow path and to enter the sheath 605, eitherthrough the fenestrations 646 upon resumption of aspiration forces orthrough the distal opening 641.

The arterial sheath 605 having one or more fenestrations 646 on thedistal end portion 643 can be delivered in combination with a deliverytool (not shown) configured to facilitate a smooth delivery into thevessel and prevent the edges of the fenestrations 646 from catching ontissue as the sheath 605 is inserted through the vessel wall. Thefenestrations 646 may also impact delivery of guidewires, ballooncatheters, or other devices through the lumen of the arterial sheath605. As such, the arterial sheath 605 can incorporate a secondary sleeveon the inside or outside of the arterial sheath 605. The secondarysleeve can be initially positioned such that the sheath fenestrations646 are covered or closed, thereby permitting smooth passage ofguidewires and other devices through the lumen of the arterial sheath605. Once the devices have been passed through the sheath, the secondarysleeve can be rotated, advanced and/or retracted to uncover or open thefenestrations. A lubricious coating of material on the inner and/orouter surfaces of the sheath 605 can be provided to improve advancementof materials. In addition, a coating of heparin can be provided todecrease the likelihood of thrombus formation on the sheath 605.

Venous Return Device

Referring now to FIG. 10, the venous return device 115 can comprise adistal sheath 910 and a flow line 915, which connects to and forms a legof the shunt 120 when the system is in use. The distal sheath 910 isadapted to be introduced through an incision or puncture into a venousreturn location, such as the jugular vein or femoral vein. The distalsheath 910 and flow line 915 can be permanently affixed, or can beattached using a conventional luer fitting, as shown in FIG. 10A.Optionally, as shown in FIG. 10B, the sheath 910 can be joined to theflow line 915 by a Y-connector 1005. The Y-connector 1005 can include ahemostasis valve 1010. The venous return device also comprises a venoussheath dilator 1015 and an introducer guide wire 611 to facilitateintroduction of the venous return device into the internal jugular veinor other vein. As with the arterial access dilator 645, the venousdilator 1015 includes a central guide wire lumen so the venous sheathand dilator combination can be placed over the guide wire 611.Optionally, the venous sheath 910 can include a flush line 1020 with astopcock 1025 at its proximal or remote end.

An alternate configuration is shown in FIGS. 10C and 10D. FIG. 10C showsthe components of the venous return device 115 including venous returnsheath 910, sheath dilator 1015, and sheath guidewire 611. FIG. 10Dshows the venous return device 115 as it would be assembled forinsertion over the sheath guide wire 611 into a central vein. Once thesheath is inserted into the vein, the dilator and guidewire are removed.The venous sheath can include a hemostasis valve 1010 and flow line 915.A stopcock 1025 on the end of the flow line allows the venous sheath tobe flushed via the flow line prior to use. This configuration allows thesheath to be prepped from a single point, as is done with conventionalintroducer sheaths. Connection to the flow shunt 120 is made with aconnector 1030 on the stopcock 1025.

In order to reduce the overall system flow resistance, the arterialaccess flow line 615 (FIG. 6A) and the venous return flow line 915, andY-connectors 620 (FIG. 6A) and 1005, can each have a relatively largeflow lumen inner diameter, typically being in the range from 2.54 mm(0.100 inch) to 5.08 mm (0.200 inch), and a relatively short length,typically being in the range from 10 cm to 20 cm. The low system flowresistance is desirable since it permits the flow to be maximized duringportions of a procedure when the risk of emboli is at its greatest. Thelow system flow resistance also allows the use of a variable flowresistance for controlling flow in the system, as described in moredetail below. The dimensions of the venous return sheath 910 can begenerally the same as those described for the arterial access sheath 605above. In the venous return sheath, an extension for the hemostasisvalve 1010 is not required.

Retrograde Shunt

The shunt 120 can be formed of a single tube or multiple, connectedtubes that provide fluid communication between the arterial accesscatheter 110 and the venous return catheter 115 to provide a pathway forretrograde blood flow therebetween. As shown in FIG. 1A, the shunt 120connects at one end (via connector 127 a) to the flow line 615 of thearterial access device 110, and at an opposite end (via connector 127 b)to the flow line 915 of the venous return catheter 115.

In an embodiment, the shunt 120 can be formed of at least one tube thatcommunicates with the flow control assembly 125. The shunt 120 can beany structure that provides a fluid pathway for blood flow. The shunt120 can have a single lumen or it can have multiple lumens. The shunt120 can be removably attached to the flow control assembly 125, arterialaccess device 110, and/or venous return device 115. Prior to use, theuser can select a shunt 120 with a length that is most appropriate foruse with the arterial access location and venous return location. In anembodiment, the shunt 120 can include one or more extension tubes thatcan be used to vary the length of the shunt 120. The extension tubes canbe modularly attached to the shunt 120 to achieve a desired length. Themodular aspect of the shunt 120 permits the user to lengthen the shunt120 as needed depending on the site of venous return. For example, insome patients, the internal jugular vein IJV is small and/or tortuous.The risk of complications at this site may be higher than at some otherlocations, due to proximity to other anatomic structures. In addition,hematoma in the neck may lead to airway obstruction and/or cerebralvascular complications. Consequently, for such patients it may bedesirable to locate the venous return site at a location other than theinternal jugular vein IJV, such as the femoral vein. A femoral veinreturn site may be accomplished percutaneously, with lower risk ofserious complication, and also offers an alternative venous access tothe central vein if the internal jugular vein IJV is not available.Furthermore, the femoral venous return changes the layout of the reverseflow shunt such that the shunt controls may be located closer to the“working area” of the intervention, where the devices are beingintroduced and the contrast injection port is located.

In an embodiment, the shunt 120 has an internal diameter of 4.76 mm (3/16 inch) and has a length of 40-70 cm. As mentioned, the length of theshunt can be adjusted. In an embodiment, connectors between the shuntand the arterial and/or venous access devices are configured to minimizeflow resistance. In an embodiment, the arterial access sheath 110, theretrograde shunt 120, and the venous return sheath 115 are combined tocreate a low flow resistance arterio-venous AV shunt, as shown in FIGS.1A-1D. As described above, the connections and flow lines of all thesedevices are optimized to minimize or reduce the resistance to flow. Inan embodiment, the AV shunt has a flow resistance which enables a flowof up to 300 mL/minute when no device is in the arterial sheath 110 andwhen the AV shunt is connected to a fluid source with the viscosity ofblood and a static pressure head of 60 mmHg. The actual shunt resistancemay vary depending on the presence or absence of a check valve 1115 or afilter 1145 (as shown in FIG. 11), or the length of the shunt, and mayenable a flow of between 150 and 300 mL/min.

When there is a device such as a stent delivery catheter in the arterialsheath, there is a section of the arterial sheath that has increasedflow resistance, which in turn increases the flow resistance of theoverall AV shunt. This increase in flow resistance has a correspondingreduction in flow. In an embodiment, the Y-arm 620 as shown in FIG. 6Aconnects the arterial sheath body 605 to the flow line 615 some distanceaway from the hemostasis valve 625 where the catheter is introduced intothe sheath. This distance is set by the length of the proximal extension610. Thus the section of the arterial sheath that is restricted by thecatheter is limited to the length of the sheath body 605. The actualflow restriction will depend on the length and inner diameter of thesheath body 605, and the outer diameter of the catheter. As describedabove, the sheath length may range from 5 to 15 cm, usually being from10 cm to 12 cm, and the inner diameter is typically in the range from 7Fr (1 Fr=0.33 mm), to 10 Fr, usually being 8 Fr. Stent deliverycatheters may range from 3.7 Fr. to 5.0 or 6.0 Fr, depending on the sizeof the stent and the manufacturer. This restriction may further bereduced if the sheath body is designed to increase in inner diameter forthe portion not in the vessel (a stepped sheath body), as shown in FIG.6B. Since flow restriction is proportional to luminal distances to thefourth power, small increases in luminal or annular areas result inlarge reductions in flow resistance.

Actual flow through the AV shunt when in use will further depend on thecerebral blood pressures and flow resistances of the patient.

Flow Control Assembly—Regulation and Monitoring of Retrograde Flow

The flow control assembly 125 interacts with the retrograde shunt 120 toregulate and/or monitor the retrograde flow rate from the common carotidartery to the venous return site, such as the femoral vein, internaljugular vein, or to the external receptacle 130. In this regard, theflow control assembly 125 enables the user to achieve higher maximumflow rates than existing systems and to also selectively adjust, set, orotherwise modulate the retrograde flow rate. Various mechanisms can beused to regulate the retrograde flow rate, as described more fullybelow. The flow control assembly 125 enables the user to configureretrograde blood flow in a manner that is suited for various treatmentregimens, as described below.

In general, the ability to control the continuous retrograde flow rateallows the physician to adjust the protocol for individual patients andstages of the procedure. The retrograde blood flow rate will typicallybe controlled over a range from a low rate to a high rate. The high ratecan be at least two fold higher than the low rate, typically being atleast three fold higher than the low rate, and often being at least fivefold higher than the low rate, or even higher. In an embodiment, thehigh rate is at least three fold higher than the low rate and in anotherembodiment the high rate is at least six fold higher than the low rate.While it is generally desirable to have a high retrograde blood flowrate to maximize the extraction of emboli from the carotid arteries, theability of patients to tolerate retrograde blood flow will vary. Thus,by having a system and protocol which allows the retrograde blood flowrate to be easily modulated, the treating physician can determine whenthe flow rate exceeds the tolerable level for that patient and set thereverse flow rate accordingly. For patients who cannot toleratecontinuous high reverse flow rates, the physician can chose to turn onhigh flow only for brief, critical portions of the procedure when therisk of embolic debris is highest. At short intervals, for examplebetween 15 seconds and 1 minute, patient tolerance limitations areusually not a factor.

In specific embodiments, the continuous retrograde blood flow rate canbe controlled at a base line flow rate in the range from 10 ml/min to200 ml/min, typically from 20 ml/min to 100 ml/min. These flow rateswill be tolerable to the majority of patients. Although flow rate ismaintained at the base line flow rate during most of the procedure, attimes when the risk of emboli release is increased, the flow rate can beincreased above the base line for a short duration in order to improvethe ability to capture such emboli. For example, the retrograde bloodflow rate can be increased above the base line when the stent catheteris being introduced, when the stent is being deployed, pre- andpost-dilatation of the stent, removal of the common carotid arteryocclusion, and the like.

The flow rate control system can be cycled between a relatively low flowrate and a relatively high flow rate in order to “flush” the carotidarteries in the region of the carotid bifurcation prior toreestablishing antegrade flow. Such cycling can be established with ahigh flow rate which can be approximately two to six fold greater thanthe low flow rate, typically being about three fold greater. The cyclescan typically have a length in the range from 0.5 seconds to 10 seconds,usually from 2 seconds to 5 seconds, with the total duration of thecycling being in the range from 5 seconds to 60 seconds, usually from 10seconds to 30 seconds.

FIG. 11 shows an example of the system 100 with a schematicrepresentation of the flow control assembly 125, which is positionedalong the shunt 120 such that retrograde blood flow passes through orotherwise communicates with at least a portion of the flow controlassembly 125. The flow control assembly 125 can include variouscontrollable mechanisms for regulating and/or monitoring retrogradeflow. The mechanisms can include various means of controlling theretrograde flow, including one or more pumps 1110, valves 1115, syringes1120 and/or a variable resistance component 1125. The flow controlassembly 125 can be manually controlled by a user and/or automaticallycontrolled via a controller 1130 to vary the flow through the shunt 120.For example, by varying the flow resistance, the rate of retrogradeblood flow through the shunt 120 can be controlled. The controller 1130,which is described in more detail below, can be integrated into the flowcontrol assembly 125 or it can be a separate component that communicateswith the components of the flow control assembly 125.

In addition, the flow control assembly 125 can include one or more flowsensors 1135 and/or anatomical data sensors 1140 (described in detailbelow) for sensing one or more aspects of the retrograde flow. A filter1145 can be positioned along the shunt 120 for removing emboli beforethe blood is returned to the venous return site. When the filter 1145 ispositioned upstream of the controller 1130, the filter 1145 can preventemboli from entering the controller 1145 and potentially clogging thevariable flow resistance component 1125. It should be appreciated thatthe various components of the flow control assembly 125 (including thepump 1110, valves 1115, syringes 1120, variable resistance component1125, sensors 1135/1140, and filter 1145) can be positioned at variouslocations along the shunt 120 and at various upstream or downstreamlocations relative to one another. The components of the flow controlassembly 125 are not limited to the locations shown in FIG. 11.Moreover, the flow control assembly 125 does not necessarily include allof the components but can rather include various sub-combinations of thecomponents. For example, a syringe could optionally be used within theflow control assembly 125 for purposes of regulating flow or it could beused outside of the assembly for purposes other than flow regulation,such as to introduce fluid such as radiopaque contrast into the arteryin an antegrade direction via the shunt 120.

Both the variable resistance component 1125 and the pump 1110 can becoupled to the shunt 120 to control the retrograde flow rate. Thevariable resistance component 1125 controls the flow resistance, whilethe pump 1110 provides for positive displacement of the blood throughthe shunt 120. Thus, the pump can be activated to drive the retrogradeflow rather than relying on the perfusion stump pressures of the ECA andICA and the venous back pressure to drive the retrograde flow. The pump1110 can be a peristaltic tube pump or any type of pump including apositive displacement pump. The pump 1110 can be activated anddeactivated (either manually or automatically via the controller 1130)to selectively achieve blood displacement through the shunt 120 and tocontrol the flow rate through the shunt 120. Displacement of the bloodthrough the shunt 120 can also be achieved in other manners includingusing the aspiration syringe 1120, or a suction source such as avacutainer, vaculock syringe, or wall suction may be used. The pump 1110can communicate with the controller 1130.

One or more flow control valves 1115 can be positioned along the pathwayof the shunt. The valve(s) can be manually actuated or automaticallyactuated (via the controller 1130). The flow control valves 1115 can be,for example one-way valves to prevent flow in the antegrade direction inthe shunt 120, check valves, or high pressure valves which would closeoff the shunt 120, for example during high-pressure contrast injections(which are intended to enter the arterial vasculature in an antegradedirection). In an embodiment, the one-way valves are low flow-resistancevalves for example that described in U.S. Pat. No. 5,727,594, or otherlow resistance valves.

In an embodiment of a shunt with both a filter 1145 and a one-way checkvalve 1115, the check valve is located down stream of the filter. Inthis manner, if there is debris traveling in the shunt, it is trapped inthe filter before it reaches the check valve. Many check valveconfigurations include a sealing member that seals against a housingthat contains a flow lumen. Debris may have the potential to be trappedbetween the sealing member and the housing, thus compromising theability of the valve to seal against backwards pressure.

The controller 1130 communicates with components of the system 100including the flow control assembly 125 to enable manual and/orautomatic regulation and/or monitoring of the retrograde flow throughthe components of the system 100 (including, for example, the shunt 120,the arterial access device 110, the venous return device 115 and theflow control assembly 125). For example, a user can actuate one or moreactuators on the controller 1130 to manually control the components ofthe flow control assembly 125. Manual controls can include switches ordials or similar components located directly on the controller 1130 orcomponents located remote from the controller 1130 such as a foot pedalor similar device. The controller 1130 can also automatically controlthe components of the system 100 without requiring input from the user.In an embodiment, the user can program software in the controller 1130to enable such automatic control. The controller 1130 can controlactuation of the mechanical portions of the flow control assembly 125.The controller 1130 can include circuitry or programming that interpretssignals generated by sensors 1135/1140 such that the controller 1130 cancontrol actuation of the flow control assembly 125 in response to suchsignals generated by the sensors.

The representation of the controller 1130 in FIG. 11 is merelyexemplary. It should be appreciated that the controller 1130 can vary inappearance and structure. The controller 1130 is shown in FIG. 11 asbeing integrated in a single housing. This permits the user to controlthe flow control assembly 125 from a single location. It should beappreciated that any of the components of the controller 1130 can beseparated into separate housings. Further, FIG. 11 shows the controller1130 and flow control assembly 125 as separate housings. It should beappreciated that the controller 1130 and flow control regulator 125 canbe integrated into a single housing or can be divided into multiplehousings or components.

Flow State Indicator(s)

The controller 1130 can include one or more indicators that provides avisual and/or audio signal to the user regarding the state of theretrograde flow. An audio indication advantageously reminds the user ofa flow state without requiring the user to visually check the flowcontroller 1130. The indicator(s) can include a speaker 1150 and/or alight 1155 or any other means for communicating the state of retrogradeflow to the user. The controller 1130 can communicate with one or moresensors of the system to control activation of the indicator. Or,activation of the indicator can be tied directly to the user actuatingone of the flow control actuators 1165. The indicator need not be aspeaker or a light. The indicator could simply be a button or switchthat visually indicates the state of the retrograde flow. For example,the button being in a certain state (such as a pressed or down state)may be a visual indication that the retrograde flow is in a high state.Or, a switch or dial pointing toward a particular labeled flow state maybe a visual indication that the retrograde flow is in the labeled state.

The indicator can provide a signal indicative of one or more states ofthe retrograde flow. In an embodiment, the indicator identifies only twodiscrete states: a state of “high” flow rate and a state of “low” flowrate. In another embodiment, the indicator identifies more than two flowrates, including a “high” flow rate, a “medium” flow rate, and a “low”rate. The indicator can be configured to identify any quantity ofdiscrete states of the retrograde flow or it can identify a graduatedsignal that corresponds to the state of the retrograde flow. In thisregard, the indicator can be a digital or analog meter 1160 thatindicates a value of the retrograde flow rate, such as in ml/min or anyother units.

In an embodiment, the indicator is configured to indicate to the userwhether the retrograde flow rate is in a state of “high” flow rate or a“low” flow rate. For example, the indicator may illuminate in a firstmanner (e.g., level of brightness) and/or emit a first audio signal whenthe flow rate is high and then change to a second manner of illuminationand/or emit a second audio signal when the flow rate is low. Or, theindicator may illuminate and/or emit an audio signal only when the flowrate is high, or only when the flow rate is low. Given that somepatients may be intolerant of a high flow rate or intolerant of a highflow rate beyond an extended period of time, it can be desirable thatthe indicator provide notification to the user when the flow rate is inthe high state. This would serve as a fail safe feature.

In another embodiment, the indicator provides a signal (audio and/orvisual) when the flow rate changes state, such as when the flow ratechanges from high to low and/or vice-versa. In another embodiment, theindicator provides a signal when no retrograde flow is present, such aswhen the shunt 120 is blocked or one of the stopcocks in the shunt 120is closed.

Flow Rate Actuators

The controller 1130 can include one or more actuators that the user canpress, switch, manipulate, or otherwise actuate to regulate theretrograde flow rate and/or to monitor the flow rate. For example, thecontroller 1130 can include a flow control actuator 1165 (such as one ormore buttons, knobs, dials, switches, etc.) that the user can actuate tocause the controller to selectively vary an aspect of the reverse flow.For example, in the illustrated embodiment, the flow control actuator1165 is a knob that can be turned to various discrete positions each ofwhich corresponds to the controller 1130 causing the system 100 toachieve a particular retrograde flow state. The states include, forexample, (a) OFF; (b) LO-FLOW; (c) HI-FLOW; and (d) ASPIRATE. It shouldbe appreciated that the foregoing states are merely exemplary and thatdifferent states or combinations of states can be used. The controller1130 achieves the various retrograde flow states by interacting with oneor more components of the system, including the sensor(s), valve(s),variable resistance component, and/or pump(s). It should be appreciatedthat the controller 1130 can also include circuitry and software thatregulates the retrograde flow rate and/or monitors the flow rate suchthat the user wouldn't need to actively actuate the controller 1130.

The OFF state corresponds to a state where there is no retrograde bloodflow through the shunt 120. When the user sets the flow control actuator1165 to OFF, the controller 1130 causes the retrograde flow to cease,such as by shutting off valves or closing a stop cock in the shunt 120.The LO-FLOW and HI-FLOW states correspond to a low retrograde flow rateand a high retrograde flow rate, respectively. When the user sets theflow control actuator 1165 to LO-FLOW or HI-FLOW, the controller 1130interacts with components of the flow control regulator 125 includingpump(s) 1110, valve(s) 1115 and/or variable resistance component 1125 toincrease or decrease the flow rate accordingly. Finally, the ASPIRATEstate corresponds to opening the circuit to a suction source, forexample a vacutainer or suction unit, if active retrograde flow isdesired.

The system can be used to vary the blood flow between various statesincluding an active state, a passive state, an aspiration state, and anoff state. The active state corresponds to the system using a means thatactively drives retrograde blood flow. Such active means can include,for example, a pump, syringe, vacuum source, etc. The passive statecorresponds to when retrograde blood flow is driven by the perfusionstump pressures of the ECA and ICA and possibly the venous pressure. Theaspiration state corresponds to the system using a suction source, forexample a vacutainer or suction unit, to drive retrograde blood flow.The off state corresponds to the system having zero retrograde bloodflow such as the result of closing a stopcock or valve. The low and highflow rates can be either passive or active flow states. In anembodiment, the particular value (such as in ml/min) of either the lowflow rate and/or the high flow rate can be predetermined and/orpre-programmed into the controller such that the user does not actuallyset or input the value. Rather, the user simply selects “high flow”and/or “low flow” (such as by pressing an actuator such as a button onthe controller 1130) and the controller 1130 interacts with one or moreof the components of the flow control assembly 125 to cause the flowrate to achieve the predetermined high or low flow rate value. Inanother embodiment, the user sets or inputs a value for low flow rateand/or high flow rate such as into the controller. In anotherembodiment, the low flow rate and/or high flow rate is not actually set.Rather, external data (such as data from the anatomical data sensor1140) is used as the basis for affects the flow rate.

The flow control actuator 1165 can be multiple actuators, for exampleone actuator, such as a button or switch, to switch state from LO-FLOWto HI-FLOW and another to close the flow loop to OFF, for example duringa contrast injection where the contrast is directed antegrade into thecarotid artery. In an embodiment, the flow control actuator 1165 caninclude multiple actuators. For example, one actuator can be operated toswitch flow rate from low to high, another actuator can be operated totemporarily stop flow, and a third actuator (such as a stopcock) can beoperated for aspiration using a syringe. In another example, oneactuator is operated to switch to LO-FLOW and another actuator isoperated to switch to HI-FLOW. Or, the flow control actuator 1165 caninclude multiple actuators to switch states from LO-FLOW to HI-FLOW andadditional actuators for fine-tuning flow rate within the high flowstate and low flow state. Upon switching between LO-FLOW and HI-FLOW,these additional actuators can be used to fine-tune the flow rateswithin those states. Thus, it should be appreciated that within eachstate (i.e. high flow state and low flow states) a variety of flow ratescan be dialed in and fine-tuned. A wide variety of actuators can be usedto achieve control over the state of flow.

The controller 1130 or individual components of the controller 1130 canbe located at various positions relative to the patient and/or relativeto the other components of the system 100. For example, the flow controlactuator 1165 can be located near the hemostasis valve where anyinterventional tools are introduced into the patient in order tofacilitate access to the flow control actuator 1165 during introductionof the tools. The location may vary, for example, based on whether atransfemoral or a transcarotid approach is used, as shown in FIGS. 1A-C. The controller 1130 can have a wireless connection to the remainderof the system 100 and/or a wired connection of adjustable length topermit remote control of the system 100. The controller 1130 can have awireless connection with the flow control regulator 125 and/or a wiredconnection of adjustable length to permit remote control of the flowcontrol regulator 125. The controller 1130 can also be integrated in theflow control regulator 125. Where the controller 1130 is mechanicallyconnected to the components of the flow control assembly 125, a tetherwith mechanical actuation capabilities can connect the controller 1130to one or more of the components. In an embodiment, the controller 1130can be positioned a sufficient distance from the system 100 to permitpositioning the controller 1130 outside of a radiation field whenfluoroscopy is in use.

The controller 1130 and any of its components can interact with othercomponents of the system (such as the pump(s), sensor(s), shunt, etc) invarious manners. For example, any of a variety of mechanical connectionscan be used to enable communication between the controller 1130 and thesystem components. Alternately, the controller 1130 can communicateelectronically or magnetically with the system components.Electro-mechanical connections can also be used. The controller 1130 canbe equipped with control software that enables the controller toimplement control functions with the system components. The controlleritself can be a mechanical, electrical or electro-mechanical device. Thecontroller can be mechanically, pneumatically, or hydraulically actuatedor electromechanically actuated (for example in the case of solenoidactuation of flow control state). The controller 1130 can include acomputer, computer processor, and memory, as well as data storagecapabilities.

FIG. 11 shows an exemplary embodiment of a variable flow control element1125. In this embodiment, the flow resistance through shunt 120 may bechanged by providing two or more alternative flow paths to create a lowand high resistance flow path. As shown in FIG. 12A, the flow throughshunt 120 passes through a main lumen 1700 as well as secondary lumen1705. The secondary lumen 1705 is longer and/or has a smaller diameterthan the main lumen 1700. Thus, the secondary lumen 1705 has higher flowresistance than the main lumen 1700. By passing the blood through boththese lumens, the flow resistance will be at a minimum. Blood is able toflow through both lumens 1700 and 1705 due to the pressure drop createdin the main lumen 1700 across the inlet and outlet of the secondarylumen 1705. This has the benefit of preventing stagnant blood. As shownin FIG. 12B, by blocking flow through the main lumen 1700 of shunt 120,the flow is diverted entirely to the secondary lumen 1705, thusincreasing the flow resistance and reducing the blood flow rate. It willbe appreciated that additional flow lumens could also be provided inparallel to allow for a three, four, or more discrete flow resistances.The shunt 120 may be equipped with a valve 1710 that controls flow tothe main lumen 1700 and the secondary lumen 1705. The valve position maybe controlled by an actuator such as a button or switch on the housingof flow controller 125. The embodiment of FIGS. 12A and 12B has anadvantage in that this embodiment in that it maintains precise flowlumen sizes even for the lowest flow setting. The secondary flow lumensize can be configured to prevent thrombus from forming under even thelowest flow or prolonged flow conditions. In an embodiment, the innerdiameter of the secondary lumen 1705 lumen is 0.063 inches or larger.

In a preferred embodiment, the connectors which connect the elements ofthe reverse flow system are large bore, quick-connect style connectors.For example, a male large-bore hub 680 on the Y-adaptor 660 of arterialsheath 110, as seen in FIG. 9B, connects to a female counterpart 1320 onthe arterial side of flow shunt 120. Similarly, a male large boreconnector 1310 on the venous side of flow shunt 120 connects to a femalecounterpart connector 1310 on the flow line of venous sheath 115, asseen in FIG. 10C. The connections can be standard female and male Luerconnectors or other style of tubing connectors.

Sensor(s)

As mentioned, the flow control assembly 125 can include or interact withone or more sensors, which communicate with the system 100 and/orcommunicate with the patient's anatomy. Each of the sensors can beadapted to respond to a physical stimulus (including, for example, heat,light, sound, pressure, magnetism, motion, etc.) and to transmit aresulting signal for measurement or display or for operating thecontroller 1130. In an embodiment, the flow sensor 1135 interacts withthe shunt 120 to sense an aspect of the flow through the shunt 120, suchas flow velocity or volumetric rate of blood flow. The flow sensor 1135could be directly coupled to a display that directly displays the valueof the volumetric flow rate or the flow velocity. Or the flow sensor1135 could feed data to the controller 1130 for display of thevolumetric flow rate or the flow velocity.

The type of flow sensor 1135 can vary. The flow sensor 1135 can be amechanical device, such as a paddle wheel, flapper valve, rolling ball,or any mechanical component that responds to the flow through the shunt120. Movement of the mechanical device in response to flow through theshunt 120 can serve as a visual indication of fluid flow and can also becalibrated to a scale as a visual indication of fluid flow rate. Themechanical device can be coupled to an electrical component. Forexample, a paddle wheel can be positioned in the shunt 120 such thatfluid flow causes the paddle wheel to rotate, with greater rate of fluidflow causing a greater speed of rotation of the paddle wheel. The paddlewheel can be coupled magnetically to a Hall-effect sensor to detect thespeed of rotation, which is indicative of the fluid flow rate throughthe shunt 120.

In an embodiment, the flow sensor 1135 is an ultrasonic orelectromagnetic, or electro-optic flow meter, which allows for bloodflow measurement without contacting the blood through the wall of theshunt 120. An ultrasonic or electromagnetic flow meter can be configuredsuch that it does not have to contact the internal lumen of the shunt120. In an embodiment, the flow sensor 1135 at least partially includesa Doppler flow meter, such as a Transonic flow meter, that measuresfluid flow through the shunt 120. In another embodiment, the flow sensor1135 measures pressure differential along the flow line to determineflow. It should be appreciated that any of a wide variety of sensortypes can be used including an ultrasound flow meter and transducer.Moreover, the system can include multiple sensors.

The system 100 is not limited to using a flow sensor 1135 that ispositioned in the shunt 120 or a sensor that interacts with the venousreturn device 115 or the arterial access device 110. For example, ananatomical data sensor 1140 can communicate with or otherwise interactwith the patient's anatomy such as the patient's neurological anatomy.In this manner, the anatomical data sensor 1140 can sense a measurableanatomical aspect that is directly or indirectly related to the rate ofretrograde flow from the carotid artery. For example, the anatomicaldata sensor 1140 can measure blood flow conditions in the brain, forexample the flow velocity in the middle cerebral artery, and communicatesuch conditions to a display and/or to the controller 1130 foradjustment of the retrograde flow rate based on predetermined criteria.In an embodiment, the anatomical data sensor 1140 comprises atranscranial Doppler ultrasonography (TCD), which is an ultrasound testthat uses reflected sound waves to evaluate blood as it flows throughthe brain. Use of TCD results in a TCD signal that can be communicatedto the controller 1130 for controlling the retrograde flow rate toachieve or maintain a desired TCD profile. The anatomical data sensor1140 can be based on any physiological measurement, including reverseflow rate, blood flow through the middle cerebral artery, TCD signals ofembolic particles, or other neuromonitoring signals.

In an embodiment, the system 100 comprises a closed-loop control system.In the closed-loop control system, one or more of the sensors (such asthe flow sensor 1135 or the anatomical data sensor 1140) senses ormonitors a predetermined aspect of the system 100 or the anatomy (suchas, for example, reverse flow rate and/or neuromonitoring signal). Thesensor(s) feed relevant data to the controller 1130, which continuouslyadjusts an aspect of the system as necessary to maintain a desiredretrograde flow rate. The sensors communicate feedback on how the system100 is operating to the controller 1130 so that the controller 1130 cantranslate that data and actuate the components of the flow controlregulator 125 to dynamically compensate for disturbances to theretrograde flow rate. For example, the controller 1130 may includesoftware that causes the controller 1130 to signal the components of theflow control assembly 125 to adjust the flow rate such that the flowrate is maintained at a constant state despite differing blood pressuresfrom the patient. In this embodiment, the system 100 need not rely onthe user to determine when, how long, and/or what value to set thereverse flow rate in either a high or low state. Rather, software in thecontroller 1130 can govern such factors. In the closed loop system, thecontroller 1130 can control the components of the flow control assembly125 to establish the level or state of retrograde flow (either analoglevel or discreet state such as high, low, baseline, medium, etc.) basedon the retrograde flow rate sensed by the sensor 1135.

In an embodiment, the anatomical data sensor 1140 (which measures aphysiologic measurement in the patient) communicates a signal to thecontroller 1130, which adjusts the flow rate based on the signal. Forexample the physiological measurement may be based on flow velocitythrough the MCA, TCD signal, or some other cerebral vascular signal. Inthe case of the TCD signal, TCD may be used to monitor cerebral flowchanges and to detect microemboli. The controller 1130 may adjust theflow rate to maintain the TCD signal within a desired profile. Forexample, the TCD signal may indicate the presence of microemboli (“TCDhits”) and the controller 1130 can adjust the retrograde flow rate tomaintain the TCD hits below a threshold value of hits. (See, Ribo, etal., “Transcranial Doppler Monitoring of Transcervical Carotid Stentingwith Flow Reversal Protection: A Novel Carotid RevascularizationTechnique”, Stroke 2006, 37, 2846-2849; Shekel, et al., “Experience of500 Cases of Neurophysiological Monitoring in Carotid Endarterectomy”,Acta Neurochir, 2007, 149:681-689, which are incorporated by referencein their entirety.

In the case of the MCA flow, the controller 1130 can set the retrogradeflow rate at the “maximum” flow rate that is tolerated by the patient,as assessed by perfusion to the brain. The controller 1130 can thuscontrol the reverse flow rate to optimize the level of protection forthe patient without relying on the user to intercede. In anotherembodiment, the feedback is based on a state of the devices in thesystem 100 or the interventional tools being used. For example, a sensormay notify the controller 1130 when the system 100 is in a high riskstate, such as when an interventional catheter is positioned in thesheath 605. The controller 1130 then adjusts the flow rate to compensatefor such a state.

The controller 1130 can be used to selectively augment the retrogradeflow in a variety of manners. For example, it has been observed thatgreater reverse flow rates may cause a resultant greater drop in bloodflow to the brain, most importantly the ipsilateral MCA, which may notbe compensated enough with collateral flow from the Circle of Willis.Thus a higher reverse flow rate for an extended period of time may leadto conditions where the patient's brain is not getting enough bloodflow, leading to patient intolerance as exhibited by neurologicsymptoms. Studies show that MCA blood velocity less than 10 cm/sec is athreshold value below which patient is at risk for neurological blooddeficit. There are other markers for monitoring adequate perfusion tothe brains, such as EEG signals. However, a high flow rate may betolerated even up to a complete stoppage of MCA flow for a short period,up to about 15 seconds to 1 minute.

Thus, the controller 1130 can optimize embolic debris capture byautomatically increasing the reverse flow only during limited timeperiods which correspond to periods of heightened risk of emboligeneration during a procedure. These periods of heightened risk includethe period of time while an interventional device (such as a dilatationballoon for pre or post stenting dilatation or a stent delivery device)crosses the plaque P. Another period is during an interventionalmaneuver such as deployment of the stent or inflation and deflation ofthe balloon pre- or post-dilatation. A third period is during injectionof contrast for angiographic imaging of treatment area. During lowerrisk periods, the controller can cause the reverse flow rate to revertto a lower, baseline level. This lower level may correspond to a lowreverse flow rate in the ICA, or even slight antegrade flow in thosepatients with a high ECA to ICA perfusion pressure ratio.

In a flow regulation system where the user manually sets the state offlow, there is risk that the user may not pay attention to the state ofretrograde flow (high or low) and accidentally keep the circuit on highflow. This may then lead to adverse patient reactions. In an embodiment,as a safety mechanism, the default flow rate is the low flow rate. Thisserves as a fail safe measure for patient's that are intolerant of ahigh flow rate. In this regard, the controller 1130 can be biased towardthe default rate such that the controller causes the system to revert tothe low flow rate after passage of a predetermined period of time ofhigh flow rate. The bias toward low flow rate can be achieved viaelectronics or software, or it can be achieved using mechanicalcomponents, or a combination thereof. In an embodiment, the flow controlactuator 1165 of the controller 1130 and/or valve(s) 1115 and/or pump(s)1110 of the flow control regulator 125 are spring loaded toward a statethat achieves a low flow rate. The controller 1130 is configured suchthat the user may over-ride the controller 1130 such as to manuallycause the system to revert to a state of low flow rate if desired.

In another safety mechanism, the controller 1130 includes a timer 1170(FIG. 11) that keeps time with respect to how long the flow rate hasbeen at a high flow rate. The controller 1130 can be programmed toautomatically cause the system 100 to revert to a low flow rate after apredetermined time period of high flow rate, for example after 15, 30,or 60 seconds or more of high flow rate. After the controller reverts tothe low flow rate, the user can initiate another predetermined period ofhigh flow rate as desired. Moreover, the user can override thecontroller 1130 to cause the system 100 to move to the low flow rate (orhigh flow rate) as desired.

In an exemplary procedure, embolic debris capture is optimized while notcausing patient tolerance issues by initially setting the level ofretrograde flow at a low rate, and then switching to a high rate fordiscreet periods of time during critical stages in the procedure.Alternately, the flow rate is initially set at a high rate, and thenverifying patient tolerance to that level before proceeding with therest of the procedure. If the patient shows signs of intolerance, theretrograde flow rate is lowered. Patient tolerance may be determinedautomatically by the controller based on feedback from the anatomicaldata sensor 1140 or it may be determined by a user based on patientobservation. The adjustments to the retrograde flow rate may beperformed automatically by the controller or manually by the user.Alternately, the user may monitor the flow velocity through the middlecerebral artery (MCA), for example using TCD, and then to set themaximum level of reverse flow which keeps the MCA flow velocity abovethe threshold level. In this situation, the entire procedure may be donewithout modifying the state of flow. Adjustments may be made as neededif the MCA flow velocity changes during the course of the procedure, orthe patient exhibits neurologic symptoms.

Exemplary Methods of Use

Referring now to FIGS. 14A-14E, flow through the carotid arterybifurcation at different stages of the methods of the present disclosurewill be described. Initially, as shown in FIG. 14A, the distal sheath605 of the arterial access device 110 is introduced into the commoncarotid artery CCA. As mentioned, entry into the common carotid arteryCCA can be via a transcarotid or transfemoral approach, and can beeither a direct surgical cut-down or percutaneous access. After thesheath 605 of the arterial access device 110 has been introduced intothe common carotid artery CCA, the blood flow will continue in antegradedirection AG with flow from the common carotid artery entering both theinternal carotid artery ICA and the external carotid artery ECA, asshown in FIG. 14A.

The venous return device 115 is then inserted into a venous return site,such as the internal jugular vein IJV (not shown in FIGS. 14A-14E) orfemoral vein. The shunt 120 is used to connect the flow lines 615 and915 of the arterial access device 110 and the venous return device 115,respectively (as shown in FIG. 1A). In this manner, the shunt 120provides a passageway for retrograde flow from the atrial access device110 to the venous return device 115. In another embodiment, the shunt120 connects to an external receptacle 130 rather than to the venousreturn device 115, as shown in FIG. 1C.

Once all components of the system are in place and connected, flowthrough the common carotid artery CCA is stopped, typically by use of atourniquet 2105 or other external vessel occlusion device to occlude thecommon carotid artery CCA. In an alternative embodiment, an occlusionelement 129 is located on the distal end of arterial access device 110.Alternately, the occlusion element 129 is introduced on second occlusiondevice 112 separate from the distal sheath 605 of the arterial accessdevice 110, as shown in FIG. 2B. The ECA may also be occluded with aseparate occlusion element, either on the same device 110 or on aseparate occlusion device.

At that point retrograde flow RG from the external carotid artery ECAand internal carotid artery ICA will begin and will flow through thesheath 605, the flow line 615, the shunt 120, and into the venous returndevice 115 via the flow line 915. The flow control assembly 125regulates the retrograde flow as described above. FIG. 14B shows theoccurrence of retrograde flow RG. While the retrograde flow ismaintained, a stent delivery catheter 2110 is introduced into the sheath605, as shown in FIG. 14C. The stent delivery catheter 2110 isintroduced into the sheath 605 through the hemostasis valve 615 and theproximal extension 610 (not shown in FIGS. 14A-14E) of the arterialaccess device 110. The stent delivery catheter 2110 is advanced into theinternal carotid artery ICA and a stent 2115 deployed at the bifurcationB, as shown in FIG. 14D.

The rate of retrograde flow can be increased during periods of higherrisk for emboli generation for example while the stent delivery catheter2110 is being introduced and optionally while the stent 2115 is beingdeployed. The rate of retrograde flow can be increased also duringplacement and expansion of balloons for dilatation prior to or afterstent deployment. An atherectomy can also be performed before stentingunder retrograde flow.

Still further optionally, after the stent 2115 has been expanded, thebifurcation B can be flushed by cycling the retrograde flow between alow flow rate and high flow rate. The region within the carotid arterieswhere the stent has been deployed or other procedure performed may beflushed with blood prior to reestablishing normal blood flow. Inparticular, while the common carotid artery remains occluded, a ballooncatheter or other occlusion element may be advanced into the internalcarotid artery and deployed to fully occlude that artery. The samemaneuver may also be used to perform a post-deployment stent dilatation,which is typically done currently in self-expanding stent procedures.Flow from the common carotid artery and into the external carotid arterymay then be reestablished by temporarily opening the occluding meanspresent in the artery. The resulting flow will thus be able to flush thecommon carotid artery which saw slow, turbulent, or stagnant flow duringcarotid artery occlusion into the external carotid artery. In addition,the same balloon may be positioned distally of the stent during reverseflow and forward flow then established by temporarily relievingocclusion of the common carotid artery and flushing. Thus, the flushingaction occurs in the stented area to help remove loose or looselyadhering embolic debris in that region.

Optionally, while flow from the common carotid artery continues and theinternal carotid artery remains blocked, measures can be taken tofurther loosen emboli from the treated region. For example, mechanicalelements may be used to clean or remove loose or loosely attached plaqueor other potentially embolic debris within the stent, thrombolytic orother fluid delivery catheters may be used to clean the area, or otherprocedures may be performed. For example, treatment of in-stentrestenosis using balloons, atherectomy, or more stents can be performedunder retrograde flow. In another example, the occlusion ballooncatheter may include flow or aspiration lumens or channels which openproximal to the balloon. Saline, thrombolytics, or other fluids may beinfused and/or blood and debris aspirated to or from the treated areawithout the need for an additional device. While the emboli thusreleased will flow into the external carotid artery, the externalcarotid artery is generally less sensitive to emboli release than theinternal carotid artery. By prophylactically removing potential emboliwhich remain, when flow to the internal carotid artery is reestablished,the risk of emboli release is even further reduced. The emboli can alsobe released under retrograde flow so that the emboli flows through theshunt 120 to the venous system, a filter in the shunt 120, or thereceptacle 130.

After the bifurcation has been cleared of emboli, the occlusion element129 or alternately the tourniquet 2105 can be released, reestablishingantegrade flow, as shown in FIG. 14E. The sheath 605 can then beremoved.

A self-closing element may be deployed about the penetration in the wallof the common carotid artery prior to withdrawing the sheath 605 at theend of the procedure. Usually, the self-closing element will be deployedat or near the beginning of the procedure, but optionally, theself-closing element could be deployed as the sheath is being withdrawn,often being released from a distal end of the sheath onto the wall ofthe common carotid artery. Use of the self-closing element isadvantageous since it affects substantially the rapid closure of thepenetration in the common carotid artery as the sheath is beingwithdrawn. Such rapid closure can reduce or eliminate unintended bloodloss either at the end of the procedure or during accidentaldislodgement of the sheath. In addition, such a self-closing element mayreduce the risk of arterial wall dissection during access. Further, theself-closing element may be configured to exert a frictional or otherretention force on the sheath during the procedure. Such a retentionforce is advantageous and can reduce the chance of accidentallydislodging the sheath during the procedure. A self-closing elementeliminates the need for vascular surgical closure of the artery withsuture after sheath removal, reducing the need for a large surgicalfield and greatly reducing the surgical skill required for theprocedure.

The disclosed systems and methods may employ a wide variety ofself-closing elements, typically being mechanical elements which includean anchor portion and a self-closing portion. The anchor portion maycomprise hooks, pins, staples, clips, tine, suture, or the like, whichare engaged in the exterior surface of the common carotid artery aboutthe penetration to immobilize the self-closing element when thepenetration is fully open. The self-closing element may also include aspring-like or other self-closing portion which, upon removal of thesheath, will close the anchor portion in order to draw the tissue in thearterial wall together to provide closure. Usually, the closure will besufficient so that no further measures need be taken to close or sealthe penetration. Optionally, however, it may be desirable to provide forsupplemental sealing of the self-closing element after the sheath iswithdrawn. For example, the self-closing element and/or the tissue tractin the region of the element can be treated with hemostatic materials,such as bioabsorbable polymers, collagen plugs, glues, sealants, dottingfactors, or other clot-promoting agents. Alternatively, the tissue orself-closing element could be sealed using other sealing protocols, suchas electrocautery, suturing, clipping, stapling, or the like. In anothermethod, the self-closing element will be a self-sealing membrane orgasket material which is attached to the outer wall of the vessel withclips, glue, bands, or other means. The self-sealing membrane may havean inner opening such as a slit or cross cut, which would be normallyclosed against blood pressure. Any of these self-closing elements couldbe designed to be placed in an open surgical procedure, or deployedpercutaneously.

In another embodiment, carotid artery stenting may be performed afterthe sheath is placed and an occlusion balloon catheter deployed in theexternal carotid artery. The stent having a side hole or other elementintended to not block the ostium of the external carotid artery may bedelivered through the sheath with a guidewire or a shaft of an externalcarotid artery occlusion balloon received through the side hole. Thus,as the stent is advanced, typically by a catheter being introduced overa guidewire which extends into the internal carotid artery, the presenceof the catheter shaft in the side hole will ensure that the side holebecomes aligned with the ostium to the external carotid artery as thestent is being advanced. When an occlusion balloon is deployed in theexternal carotid artery, the side hole prevents trapping the externalcarotid artery occlusion balloon shaft with the stent which is adisadvantage of the other flow reversal systems. This approach alsoavoids “jailing” the external carotid artery, and if the stent iscovered with a graft material, avoids blocking flow to the externalcarotid artery.

In another embodiment, stents are placed which have a shape whichsubstantially conforms to any preexisting angle between the commoncarotid artery and the internal carotid artery. Due to significantvariation in the anatomy among patients, the bifurcation between theinternal carotid artery and the external carotid artery may have a widevariety of angles and shapes. By providing a family of stents havingdiffering geometries, or by providing individual stents which may beshaped by the physician prior to deployment, the physician may choose astent which matches the patient's particular anatomy prior todeployment. The patient's anatomy may be determined using angiography orby other conventional means. As a still further alternative, the stentmay have sections of articulation. These stents may be placed first andthen articulated in situ in order to match the angle of bifurcationbetween a common carotid artery and internal carotid artery. Stents maybe placed in the carotid arteries, where the stents have a sidewall withdifferent density zones.

In another embodiment, a stent may be placed where the stent is at leastpartly covered with a graft material at either or both ends. Generally,the stent will be free from graft material and the middle section of thestent which will be deployed adjacent to the ostium to the externalcarotid artery to allow blood flow from the common carotid artery intothe external carotid artery.

In another embodiment, a stent delivery system can be optimized fortranscervicaltranscarotid access by making them shorter and/or morerigid than systems designed for transfemoral access. These changes willimprove the ability to torque and position the stent accurately duringdeployment. In addition, the stent delivery system can be designed toalign the stent with the ostium of the external carotid artery, eitherby using the external carotid occlusion balloon or a separate guide wirein the external carotid artery, which is especially useful with stentswith sideholes or for stents with curves, bends, or angulation whereorientation is critical.

In certain embodiments, the shunt is fixedly connected to the arterialaccess sheath and the venous return sheath so that the entire assemblyof the replaceable flow assembly and sheaths may be disposable andreplaceable as a unit. In other instances, the flow control assembly maybe removably attached to either or both of the sheaths.

In an embodiment, the user first determines whether any periods ofheightened risk of emboli generation may exist during the procedure. Asmentioned, some exemplary periods of heightened risk include (1) duringperiods when the plaque P is being crossed by a device; (2) during aninterventional procedure, such as during delivery of a stent or duringinflation or deflation of a balloon catheter or guidewire; (3) duringinjection of contrast. The foregoing are merely examples of periods ofheightened risk. During such periods, the user sets the retrograde flowat a high rate for a discreet period of time. At the end of the highrisk period, or if the patient exhibits any intolerance to the high flowrate, then the user reverts the flow state to baseline flow. If thesystem has a timer, the flow state automatically reverts to baselineflow after a set period of time. In this case, the user may re-set theflow state to high flow if the procedure is still in a period ofheightened embolic risk.

In another embodiment, if the patient exhibits an intolerance to thepresence of retrograde flow, then retrograde flow is established onlyduring placement of a filter in the ICA distal to the plaque P.Retrograde flow is then ceased while an interventional procedure isperformed on the plaque P. Retrograde flow is then re-established whilethe filter is removed. In another embodiment, a filter is placed in theICA distal of the plaque P and retrograde flow is established while thefilter is in place. This embodiment combines the use of a distal filterwith retrograde flow.

Although embodiments of various methods and devices are described hereinin detail with reference to certain versions, it should be appreciatedthat other versions, embodiments, methods of use, and combinationsthereof are also possible. Therefore the spirit and scope of theappended claims should not be limited to the description of theembodiments contained herein.

1. A system for treating a carotid artery, comprising: an arterialaccess device wherein the access device includes a distal sheath adaptedto be introduced into a carotid artery through a penetration in a wallof the carotid artery, the sheath having a distal end adapted to beintroduced into the common carotid artery, a proximal end, and a lumenextending between the distal and proximal ends and communicating with adistal opening and a proximal opening; wherein the distal sheath is atleast partially formed of a reinforcement material that defines aplurality of spaces; and wherein the distal sheath includes a pluralityof fenestrations and wherein at least one of the fenestrations alignswith one of the spaces of the reinforcement material.
 2. A system as inclaim 1, wherein the distal sheath includes a distal portion and whereinall the fenestrations are contained entirely within the distal portion.3. A system as in claim 1, wherein the distal sheath includes a distalportion and wherein at least one of the fenestrations is containedwithin the distal portion.
 4. A system as in claim 1, wherein thefenestrations are distributed longitudinally or circumferentially alongthe distal portion.
 5. A system as in claim 1, further comprising astopper member that covers a portion of a distal section of the distalsheath such that a portion of the distal section of the sheath iscovered by the stopper member and an exposed portion of the distalsection of the distal sheath is exposed, wherein the stopper member,when coupled to the distal sheath, limits insertion of the distal sheathinto the carotid artery to the exposed portion
 6. A system as in claim1, wherein the stopper member is removable from the distal section ofthe distal sheath.
 7. A system as in claim 5, wherein the fenestrationsare at least partially positioned within the exposed portion of thedistal section of the distal sheath.
 8. A system as in claim 5, whereinthe fenestrations are entirely positioned within the exposed portion ofthe distal section of the distal sheath.
 9. A system as in claim 1,wherein the reinforcement material comprises at least one of aspiral-wound ribbon, a braid, and a mesh.
 10. A system as in claim 9,wherein the spaces of the reinforcement material are formed of gapsbetween individual coils or a holes through a braid or a mesh.
 11. Asystem as in claim 1, further comprising a sleeve mechanically coupledto the distal sheath, wherein the sleeve moves between a first positionthat covers the fenestrations to prevent fluid flow therethrough and asecond position that does not cover the fenestrations.
 12. A system asin claim 11, wherein the sleeve is positioned inside the distal sheath.13. A system as in claim 11, wherein the sleeve is positioned outsidethe distal sheath.
 14. A system as in claim 11, wherein the sleeverotates between the first and second positions.
 15. A method fortreating a carotid artery, comprising: positioning an arterial accessdevice having a distal sheath into a common carotid artery through anaccess location in a neck of a patient, the arterial access devicecomprising: a distal sheath adapted to be introduced into a carotidartery through a penetration in a wall of the carotid artery, the sheathhaving a distal end adapted to be introduced into the common carotidartery, a proximal end, and a lumen extending between the distal andproximal ends and communicating with a distal opening and a proximalopening; wherein the distal sheath is at least partially formed of areinforcement material that defines a plurality of spaces; and whereinthe distal sheath includes a plurality of fenestrations and wherein atleast one of the fenestrations aligns with one of the spaces of thereinforcement material; occluding blood flow at an occlusion location ofthe common carotid artery so as to establish retrograde blood flowthrough the common carotid artery such that blood flows into the lumenof the arterial access device, wherein the occlusion location is locatedproximal of the distal opening of the distal sheath so as to form a zonebetween the occlusion location and the distal opening; wherein the bloodflows into the distal sheath via at least one of the distal opening andthe fenestrations.
 16. The method of claim 15, wherein the arterialaccess sheath includes a removable stopper member that covers a portionof the distal section of the sheath such that a portion of the distalsection of the sheath is covered by the stopper member and a portion ofthe distal section of the sheath is exposed, wherein the stopper member,when coupled to the sheath, limits insertion of the sheath into thecarotid artery to the exposed portion, and further comprising: insertingno more than the exposed portion of the sheath into the common carotidartery.
 17. The method of claim 16, wherein the fenestrations arelocated entirely within the exposed portion of the distal sheath. 18.The method of claim 15, wherein the zone is a static zone.
 19. Themethod of claim 15, further comprising positioning the distal sheath sothat at least one of the fenestrations is positioned in the zone. 20.The method of claim 15, wherein occluding blood flow at an occlusionlocation comprises applying a vascular clamp at the occlusion location.21. The method of claim 15, wherein occluding blood flow at an occlusionlocation comprises expanding a balloon at the occlusion location. 22.The method of claim 15, further comprising making a transcervicalincision to expose a region of a common carotid artery at the accesslocation.